You can bulk import your favorite senders from Gmail. This gives you a boost when you start using the Screener, as you will not need to explicity allow these senders - they will land in your inbox from day one.
Export your favorite contacts from Gmail
Visit Gmail and click the dots menu at the top right of the page. Click "Contacts".
When the contacts page loads, click "Frequently Contacted" on the left hand side:
Select one of the contacts and then you will see a dropdown select at the top of the page, click "All" to select all of the senders.