The official Git documentation includes the Git manual pages (reference) and an online Git book to help you get started. There are also videos, cheat sheets, and a pile of links to other Git tutorials and books.
Some developers find SmartGit to be a useful GUI based application for managing local Git repositories.
Please contact one of our engineers for assistance using Git with the Serval Project. They are happy to help with specific problems, but will not provide general instruction that could be gleaned from any of the above resources.