Guide to Processing Tabular Coordinate Data with ArcMap
First make sure that the tabular data you are hoping to work with is saved as a CSV (comma separated values) file and contains X and Y coordinate information for point features that you can successfully represent on a map. If you data is saved in some other file format, like XLSX, open the spreadsheet and save it out as a CSV file. Next verify that your coordinates are stored correctly in two separate columns. Coordinates saved in a spreadsheet are typically coordinates expressed in latitude and longitude, but could also be northings and eastings identifying locations in a specific UTM or state plane coordinate system. If your coordinates are listed together in a single column and are separated by a comma or space (like "30.102, -45.215"), split up your coordinates into two separate columns named X and Y. If you have a large number of rows to process, the Text to Columns tool located under the Data tab can help facilitate this process. When you are splitting up coordinate pair values into separate columns also make sure that have determined whether your coordinates are ordered X,Y or Y,X as your data will not map correctly when loaded into GIS software if these values are mixed up. Once your coordinate fields are named X and Y respectively, each column contains the correct coordinate values (e.g. the X column contains longitude or easting values, the Y column contains latitude or northing values), and your spreadsheet is saved as a CSV you are ready to move on to step 2.
Open up ArcMap. Use the Catalog pane to navigate to the location of the CSV on your file system (note that you may need to establish a new folder connection in Catalog to access the location on your computer where the CSV is stored) and then drag the CSV into your map pane. You should see your CSV show up in your table of contents but you will notice that no points appear in the map. If the coordinates that you want to map are written in your CSV as coordinates of latitude and longitude you do not need to worry about adjusting your data frame coordinate system and can go ahead and skip the next step. If your coordinates represent northings and eastings in either a UTM or state plane coordinate system however (like UTM Zone 14N or State Plane Texas Central), make sure that you follow the instructions in the next step so that your data shows up correctly when mapped.
If your coordinates do not represent degrees of latitude and longitude you will need to figure out what unit of measurement they represent (meters or feet) and what coordinate system (like a UTM or state plane zone) they correspond to. Once you have determined the unit of measurement and coordinate systems your coordinates refer to, right click on Layers in your ArcMap table of contents and select Properties from the context menu that appears to pull up your data frame properties window. In this window, click on the Coordinate System tab, then either search for or browse for the correct coordinate system for your data. Once you have found the name of the correct coordinate system, click on it to hightlight it and then click OK to assign that coordinate system to your data frame. You can now move on to the next step.
Right click on the name of your CSV in your ArcMap table of contents and, in the context menu that appears, click on Display XY Data. This will bring up the Display XY Data window where you should see that your X field from your spreadsheet is automatically selected for the X Field: parameter and your Y field from your spreadsheet is automatically selected for the Y Field: parameter as shown in the screenshot below. If you do not see this showing up correctly, using the dropdown field selectors to many choose the X and Y fields respectively for these parameters. If the x and y fields do not show up in the dropdown field selects, this is an indication that something went wrong with one of the previous steps in this process and the coordinate information in your CSV may not be structured correctly - try reopening the CSV and starting again at step 1 to see if you can fix the issue. Once your X and Y field parameters are correctly selected and match the screenshot below, click OK to proceed (if you see a warning message at this point about a missing Object ID field you can just click OK and ignore it).
You should now see your points show up in your map pane. It is a good idea at this stage to load a basemap or other dataset for your study area into your map document to make sure the points created from your CSV's coordinate data are showing up in the correct place on Earth. If you find that they are not showing up where you expect, it is likely that something went wrong at some stage of the process and you will want to review these steps to see if you can fix the problem. The most ommon issues that cause points to show up in the wrong place on Earth are the X and Y coordinates being mixed up and the wrong coordinate system being selected for the project data frame so make sure you check and verify that these are not the cause of the problem. If your points are showing up where you expect then to, proceed to the following step.
Now that your points are showing up correctly in your map it might be tempting to stop reading here and move on with the rest of the work you have planned for your project, but there is one more step you have to complete to avoid running into problems down the road. The points you see in the map actually just being read from your CSV by your GIS software and stored in memory on your computer - they have not yet been saved as a geospatial file type. In order to save your data in a geospatial format like a shapefile or feature class in a file geodatabase, you will need to first right click on your new points layer in your table of contents (it should have the same name as your CSV but will also include the word " Events" at the end), click "Data > Export Data" in the context menu that appears to bring up the Export Data window shown below. In this window, under the words "Use the same coordinate system as:" you should click the radio button for the data frame. You should also click the yellow folder icon to choose where you want the data to be saved, choose whether to save the data as a shapefile or feature class, and choose the name of the exported file. Once you have configured these saving options, click OK to finish the process - the data from your CSV should now be correctly saved in a geospatial format that will allow you to easily map the points defined by your coordinate pairs.