You should always have multiple copies of your work. You can have one on your computer or laptop and another on Box, Dropbox, email, or a usb drive. Since you will be using GitHub to submit assignments, it is strongly recommended that you frequently push to your repository as your off-site backup.
git add -pto review and add all your changes to tracked files.
git statusto see whether there are any untracked files that should be added. If there are, add them.