Go to https://github.com/VandyFOSS/documentation
Click fork in top right
Select your username
Should redirect you to the new fork. If not, go to github.com/username then click documentation.
Go to the file sandbox.md, and press the pencil. Make a change.
At the bottom of the file, select create a new branch.
Select "base: master" in the dropdown. It should be selected already, but doing so will make "compare across forks" show up above. Click compare across forks, and select the following options:
base fork: VandyFOSS/documentation
base: master
head fork: username/documentation
compare: patchname
Click create pull request.
Write a message.
Click create pull request.