There are different methods of logging in to cPanel on web.illinois.edu for University of Illinois members and for external partners and collaborators.
If prompted, choose your Illinois.edu email and log in with your NetID and NetID password.
The sign-in sequence
First, you'll be prompted for a Microsoft login.
Then you'll see the Illinois identity window.
Finally, you'll be given the choice of whether to stay logged in for longer periods of time.
In order to be able to log in to a particular website, your campus partner will need to have given you access either to that site or to the cPanel account as a whole.
If you do need to log in to the cPanel account itself:
If prompted, choose the Gmail account that you gave to your campus partner and follow Google's prompts.