Imo I would dump that and build something simpler from scratch, look for tutorials on adding an admin area. This app is complicated with basically no documentation whatsoever on how to use it. You’re supposed to grab all the code, then build on top of it, but there’s close to zero information on how to do that. The best I can come up with re how to use it is this:
I realise this isn’t a super helpful answer, I’ll see if I can dig around and find something that might be helpful