The Toolkit uses Google Documents for most sample assignments. You can work with these assignments in a number of ways. If you have a Google account, clicking "file" -> "make a copy" once you have opened a Google Document will add a copy of the file to your Google Drive account. You can make any needed edits to this new file.
If you do not have a Google Account, use the download link under each assignment to download a copy to your computer or click "file" -> "download as" once you have opened a Google Document. You can make any needed edits to the downloaded file.