How can I use a theme as my WP theme?

I had purchased a theme so I could use their theme (I am essentially a virgin to wordpress) and what I would like to do is use the theme ( as my Wordpress theme. Is this possible and how can I go about incorporating THEIR theme into my WP installation? I just purchased the one-month to give you guys out a try, you have quite a few nice plugins, including the WHMCS ones - thats what sold me.

Look forward to your reply.