I have been using SVN for the past few years, but I decided to start transitioning to GIT. Below are a few links to help me keep track of what I have learned.
To install git on our server you can follow the following tutorial https://help.ubuntu.com/lts/serverguide/git.html. Overall the process is fairly straight forward and well document. If you are receiving a password prompt that means that (most likely) you did not setup the ssh key properly. You need to generate your local private/public key, and then add to the server. After that you should be ready to go. To test that this works, you should be able to ssh into the git account without requiring a password.
To include multiple projects (e.g., you may need to do this when you are including someone else’s library) you might consider using submodules http://git-scm.com/book/en/v2/Git-Tools-Submodules. However, subtree seems to be a better way to go. Below are a few articles discussing differences: