This is a really great question. Suprisingly, when I was still in university- so many students including my self had a tough time understanding github's work flow. It seemed that the kids who knew what git commands to do were memorizing some trick I had no idea about.
There's a couple of really great references to help you get started and navigate your way through git's workflow. The best post out there is by one of the founder's of Github. He posted this article, "Github Flow". It's a must read and will really clarify alot of the inner workings of your workflow in relation to github and will also suggest best practices. The second one is called "A successful Git branching model". This one also outlines the fundamentals of feature and branch management. I don't want to specifically reccommend doing a git stash or a git pull or a git push. Because I don't know exactly what the status of your branches are right now. I also belive in the Etymology, "if you give a man a fish he is hungry again in an hour. If you teach him to catch a fish you do him a good turn" haha.
I promise you those two articles will really help you solidify your understanding of git's distributed revision control and source code management system.
Please let me know if you have any questions!
git statusshow you? Also, did you commit your changes that you made?