The first screen you and your users will see when accessing the built-in MyCourts website is the Login Screen:
If the user has never logged on before, or you haven't already created a user account for them in MyCourts -> Membership, the new user will need to select the Create Account link. That will open a basic form that the new user will need to complete:
Once they complete the form they need to select 'Create Account'. If all is in order, the account will be created and they will be sent an email. The new user will need to click a link in the email sent to them to activate the account. Once they have activated their account they will be able to login.
The defaults for the new user are all defined in MyCourts Administrator. This allows you to grant them various access rights depending on their default membership level etc:
If you create the new user manually in MyCourts -> Membership then don't forget to manually mark their Internet Details as 'confirmed':