Following Unity’s Github tutorial, it says to download the GitHub for Unity asset from the asset store and import it, from there open the github window by going to Window > GitHub. However no such option exists on the dropdown
Sounds like you have some compile errors that prevent the plugin from loading. What does it say in the console?
btw, it seems the plugin is currently in limbo. No one on GitHub’s side seems to be working on it anymore, Unity made a fork called Git for Unity but its developer said in a ticket that he only works on it in his personal time.
I do hope that Unity will allocate resources for it and continue its development but right now the project hasn’t seen a proper update in almost a year.
That’s the thing though, no errors whatsoever, I even made a new project where the only thing I did was import Github and it didn’t work.