Github itself is a great place to share your code and collaborate with other people!
Git is great but can be tricky at the beginning.
There are a few things you need to get your head around , there are new concepts and "jumping" to the command section without reading the introduction is not always a good idea, you'll have to go back to it.
The one thing that really helped me was this two videos here that I would strongly recommend you to watch.
I am the kind of guy that is suffering to sit at the chair watching a video for 2 hours but if you are struggling with GIT this is worth it.
Also another great resource is think like a git
Once you are more familiar with the concepts (you can just jump to the command section) other good references are
- git community book,
- everyday git
- guide on stackoverflow
- Git questions on stackoverflow sorted by votes