Step 1. Fork the class repo (https://github.com/stat201/diary2.git) to your own account, and create a local clone of it on your computer to make changes. Instructions on how to do so can be found here: https://help.github.com/articles/fork-a-repo/
Step 2. Pick your favorite diary entry since Feb 16, save it as "YourFirstName_YourLastName.txt" in the local clone on your computer. (Note: adding this file is the only contribution you need to make. Do not set up branches, etc.)
Step 3. Push this change to your account. For this you'll be using commands such as "git add", "git commit", "git push" etc. A comprehensive reference for these can be found here: http://gitref.org/basic/ and https://help.github.com/articles/pushing-to-a-remote/
Step 4. Create a pull request to the class repo so that your change will be synced. Instructions here: https://help.github.com/articles/creating-a-pull-request/
(optional) Step 5. Keep your fork up-to-date with the class repo when everyone is finished contributing to it. Instructions here: https://help.github.com/articles/syncing-a-fork/ If you wish, on command line cd into your local clone folder and type "sh aggr_diary.sh", which gives you a file aggregating everyone's favorite dairy entry (located outside of the current folder.)