The definitive book on git is: [Cha14] You may download it from: http://www.git-scm.com/book/en/v2 or you may read it online at that address. You are expected to familiarize yourselves with chapters 1 - 6 of that book.
Documentation and tutorial from the horse's mouth: gittutorial(7). This is the manual page for the git software. Quite readable and paedagogical. Do not fear the command line when you work with git. As a daily reference when you forget the commands Everyday GIT With 20 Commands Or So.
My own slides at http://wetware.work/prez/introducinggit/ leaning heavily on the excellent video: Engineer Man: Git Source Control for the Impatient