This feature is available in BroadFast Autoresponder PRO version. The idea is to charge for premium content, downloads etc.
First, as usual create your mailing list. Then click on the link in the popup that says: "Configure as premium (paid access) mailing list":
Check the checkbox and set your currency and price.
If you have not yet done so, set your payment options following the link "payment options" as shown above.
You'll see the following page:
For Paypal it's enough to insert your Paypal ID. The buttons and the automated payment notification will be handled by the software.
For other payment options just insert the HTML code for the payment links or payment buttons. You may need to activate manually the members who pay through these other payment methods.