Just make it in the same way you made the first site:
* Download the "Open Source" edition from here:
Upload it to your new domain location then visit that domain, the install script will run and you enter the database credentials ..... Create the first user, that will be your admin user who can access the ACP....... go to the ACP -> CORE -> MARKETPLACE -> TOOLS -> MARKETPLACE CHANNELS -> (jamroom) -> MODIFY
Then put in your premium license key found under the "Your marketplace settings" here:
Once thats done all the modules will nave no price on them in the MARKETPLACE you should just see INSTALL instead of a price to buy.