Reassign license spot

I have a 10 user license for a client and one of their employees quit. Their computer was wiped clean. I want to remove this user from the license so I can use it on the new employee. I see there is a website link to go in and adjust the license. However, In the login it specifically asks for “Group”. I have no idea what that is. How do you login to do this?

The group is usually User (capital U)

If that does not work, click on the Reset password link and it will resend the login credentials.