Now that you've ensured that ProductCart can successfully communicate with MailUp, return to the MailUp Integration home page. To do so, select Customers > MailUp Integration. You should see the following page.
From the menu, click on Retrieve and Manage Lists. ProductCart will connect to your MailUp Console and retrieve all lists that have been added to the system. By default your MailUp console contains at least one list. For a definition of what a LIST is in the MailUp system, click here.
Once all lists have been imported into ProductCart, a new screen will be shown. On this screen you can:
If you have more than one list in your MailUp console, this translates into the ability for your customers to subscribe and unsubscribe to/from multiple newsletters.