I don't know any developers using Git on Windows ... that may be the root of the documentation issue.
I can recommend that you not worry about using the command-line (the black box) and to instead try one of the many GUI clients out there. eg http://www.makeuseof.com/tag/5-windows-git-clients-git-job/
TortoiseGit might be the simplest alternative that will be enough to easily "fetch" an initial copy of the current Moodle repository into your home directory and then "pull" updates of new versions whenever you want to. All the rest is really only useful if you are editing code and sharing those edits.
Perhaps someone else might like to contribute some detailed instructions to this discussion as I don't have Windows handy. This looks like a good start. When it comes time to enter the Moodle git repository, use git://git.moodle.org/moodle.git and choose the MOODLE_23_STABLE branch.