I want to buy a new license. What should I do?

I want to change my login email address. I need to add or remove user under our account. How? I need to add/remove/update users who have access to licenses or can submit/review tickets. I forgot my password and want to recover it. I want to change my password. Why do I see "No valid license" on a particular version in the Customer Portal? How do licenses work? What should I do to renew after I pay maintenance? What are RETIRED and EOL (End-Of-Life) versions? User X is a part of my team but cannot see our licenses/tickets. Why? How can I assign my license to someone else? I cannot log in, yet I’m convinced I have the right log in details.