How to use Git?
Solution 1:
Have a look at git for designers for great one page article/high level intro to the topic. (That link is broken: Here is a link to another Git for Designers )
I would start at http://git-scm.com/documentation, there are documents and great video presentations for non-software-developer/cs users. Git for beginners have some basic stuff.
Solution 2:
I really like the O'Reilly book "Version Control with Git". I read it cover-to-cover and now I'm very comfortable with advanced git topics.
Solution 3:
git clone your-url local-dir
to checkout source code;
git pull
to update source code in local-dir;