In order to get started, you're going to have to use the command line.
First you'll want to initialize a local repo in place. cd to the folder your files that you want under version control and issue:
git init
You've now initialized a git repository in that foleder. Now you need to add all of the files to it:
git add .
git commit -m "Initial Import"
Now cd to the parent folder of your local repository. You're going to want to make a "Bare" clone of the repository to act as your central repo. Issue the following command:
git clone projectFolder/ ProjectName.git
ProjectName.git will be created with only the version control repository. Move this folder to wherever you want to act as your central repository. From there on out, you can clone and pull from the central repository and push to the central repository.
To clone from a central repository via SSH:
git clone [user@]host.xz:/path/to/repo.git/
Or, if your repo is on a network share
git clone D:/path/to/repo.git/
This is also doable from the GUI client for checking out and pushing changes back to the repo.