TL ; DR
Form a team (5 members)
Come up with a project idea
web / mobile application (also possible: smart watch app, VR - talk to us)
Think of a typical use - a need that could be answered by you application
Maybe something you always wanted to create...
Discuss it with us by email
Email:
[email protected]
Open a project web site
Start at: https://github.com/repositories/new
This will serve as your project home page
License: choose the one that suits you best (this might help), if you can't
decide choose Apache V2
Learn JavaScript
It will become very useful very soon