Provide some github UI info for tasks on issues and PRs #16
Description
Tasks S,T,U,V,W,X (Issues and PRs at 2502047) require some more hand-holding, possibly with GitHub UI screenshots, because the UI has become quite unwieldy for newcomers.
Another important thing that warrants an explicit warning is that GitHub is quite stubborn in forcing users to make PRs against upstream instead of against the fork.