This is probably not the primary way people use the tool, but if I log in (desktop, Chrome on macOS), click "Start a board" on the sidebar, and go to click any of the inputs, I can't type text in them (the inputs are "Start from an example", "What are you building", and "The brief".
If you scroll down they want you to "Connect copperhead to GitHub first." The bottom should have a page where you can give them access to a repo for handling stuff.