Go to "Manage Resources" (/admin/manageresources) and click on the title of the resource you want to edit
Select a membership from the dropdown and save changes.
After adding the first membership you can add additional ones.
There is a setting under advanced features where you can decide to have people either supended when they cancel their subscription, or to have it where it doesn't cancel it right away, but instead it cancels it when it is scheduled to end. If it is set to to suspend when their susbscription would have ended, instead of instantly, then what happens is anyone without a payment will be suspended. You would have to manually add a payment for the member to prevent them from being suspended.
A member is suspended when their payment is canceled. Our software is notified by an IPN when a subscription is canceled and the member is suspended immediately. There is a setting that can be turned on to have them suspended when their next payment would have been due, but by default this is turned off, and this should be used carefully because it will suspend anyone that doesn't have a payment record.