Setting up Paypal for imported member base

Hi everyone,
I thought I saw this answered once before, but couldn't find it. I just got around to working with aMember. I have version 2.3.4PRO. I have already imported my member base from my own system to aMember. I am now in the process of going over each account to make sure everything imported in correctly and add product/subscription information for them. Most of my members fall under three payment types: free, mail-in and PayPal. For the ones already on Paypal subscriptions, how do I setup aMember to recognize this? I am sure I probably have to put their PayPal Subscription ID somewhere, or something else that links their current PayPal subscription to aMember.
Thanks,
Rick

Thanks Alex,
Just to make sure I understand you.
1. Go into Paypal and do a download of subscriptions for, lets say, the past year.
2. Go into aMember and do an import. Do I fill out the top section on page one or just the bottom section? If I have to fill out the top section, will the import re-create all my current members, or will it just update them with their PayPal subscription information?
3. I have changed the subscriptions, so the subscriptions in aMember won't match the subscription names from Paypal. After they are imported, do I just go in and change what the subscription package was called in Paypal to the new subscription package is called is aMember? I am assuming that it doesn't matter as long as the Subscription IS from Paypal is there, correct?

Thanks for your help.
Rick