This thread is for a different repo but I attached Troys instructions for the redwizard for you.
Not sure how familiar you are with the process but i recommend following Troy’s steps and if you have a problem after that, follow up with questions.
It looks like you added the repo url correctly. The “/” is usually added at the end automatically so its not the issue. The problem could be your vpn, not allowing from unknown sources or something else entirely.
Edit: I tested the url and it’s working for me. I didn’t DL the wizard but source was added as zip file w/o issue.