[Hosting] premium hosting

your sign up page says that on trial I can try out premium hosting.
I want to try it.
Do I need to do anything special, or do I just go to
and begin by adding a temporary domain?
if my site is called
do I enter in the space for the temporary domain
or do I enter something else? If so what?
thank you for the help
If I keep premium, what will it cost?