If I am understanding this correctly (I'm probably not), You go to the Git tab in Studio, select Launch Git UI (?). When i do that I get a small window with a red X button graphic and nothing else. I was thinking it would have a window to enter in the commands/ code you mention, I don't seem to get that.

Yes, as far as I know.

Where and how did you get the Git plugin for Studio? This is what we thought might be the solution. But we thought we had already installed any extensions/ add-ons needed.

Thank you  to all who have responded so far. I still haven't explored all the references and links but find I am missing some answers I am looking for. First, I already have a developed (large) application where we have been manually performing source control. We want to move it into a repository in Git. Most of the information is about putting single new program into Git. How do I load the entire existing library? Second, is there something explains each of the Git options: Status, Settings, Launch Git UI, Push to remote branch, Fetch from remote, Pull changes from remote branch, Create a new branch, Check out an existing branch, Export All, Export All (Force), Import All, Import All (Force).