1) Login to your Admin CP of your current Premium forum.
2) Under JFH Resources click Premium Service
3) Under Premium Service scroll down until you see add premium forums click on it!
4) Input the information for your other jcink forum you wish to apply premium services to. Here's the catch, you have to be the primary admin/owner for both of these forums for the premium service to be applicable to both! You will put in your e-mail and login for the other forum
5) Voila! When you log into your other forum you will now have the same premium service options!