If i am not mistaken the same way. As it's a addon you will see all domains added to the account. If you want to restrict access to only that domain you will need to make a seperate user.
Not totally sure but this is what i have experienced.
Hello, http://ipaddress/~username is the correct way but first You have to set the domain You want to access in that way to be the default domain for the account. At least I think this is the way to do it.