Like Lesley, I used this document as a guide for installing TortoiseGit. Note in the pre-requisites that you should install Git for Windows before installing TortoiseGit. I did NOT need to download the Windows Installer 4.5.
Then I used these directions to generate and save the SSH keys needed to commit code without using a password every time. The directions worked perfectly, except for Step 3. Right before #2 in Step 3 (Add key), I had to insert an additional command from this website:
To CLONE a local copy of a repository (i.e. download a copy of the code to your computer), you will need the repository url. This can be found online on the right-hand side of a repository's web page. Keep in mind that currently all the succession extensions are grouped together so the url to download the code is here. Right now, you have to download the code for ALL the succession extensions to be able to modify one of them.
Like with Torroise SVN, you make a folder on your computer, then right click on it to pull up a drop-down menu. Click on Git Clone, which will pull up a menu that will prompt you for the GitHub repository URL. Hit OK and it should start downloading the code.
To commit your changes to the GitHub repository, click on the folder and click on Git Commit... Master. When that's finished, click on Git Synch and click on Push to "push" your revised code back to GitHub