Need to add current paper magazine subscribers to forums

[FordMustang]

We have converted over to vBulletin as our host for Legendary Ford Magazine. We've converted form a paper magazine to all digital. Overall I'm pleased with vBulletin--though the learning curve for a N00b is steep.

I have an issue that is problematic. I have 4,000 people that paid for the paper magazine and need to be converted over to our vBulletin site. Some of them are 1 year subs, some are 2 year subs etc. How can I put them in and have termination dates on these subscriptions? Obviously I don't want them to pay again and when I tried to make a zero dollar amount subscription in the Paid Subscription forums it would not let me.

Someone with some knowleged PLEASE help.

Jeff