Adding subscribers is simple no matter wether you are importing from a spreadsheet, adding them one by one or importing from another service.
The following guide covers adding subscribers to your group with just a few clicks...
Click the Subscribers tab at the top of the MPZMail Control Panel
Make sure you have added at least one group. Now click on the group name towards the left of the page. This will take you into the group view where you can do a lot of things, one of which is adding new subscribers.
From the "View Group" page you are now on, click the "Add Subscribers" sub menu item towards the top of the page.
There are now three options, enabling you to add subscriber in different ways.