For those new to GitHub, and I am one, it’s very well documented. First a quick overview of the process.
Open Live Writer has two different repositories (a repository is just a place to store things). One for the program itself and a second one for the documentation. If you are reading this, you are reading documentation.
The code is at https://github.com/OpenLiveWriter and the documentation is https://github.com/OpenLiveWriter/OpenLiveWriter.Github.io
Unfortunately if you are adding to documentation or code, you do have to use both GitHub desktop and Git Shell, again the process for both are very well documented, with a tutorial loaded into Github Desktop.