Click "New Supplier":

Enter the Supplier information:

You can also search for the FFL if you know the zip code and business name. This will autofill the known contact details. 

EDIT SUPPLIER

Click on the "Edit" next to the supplier you want to edit:

Modify the information and click Save:

DELETE SUPPLIER

Select the Supplier and then select Delete:

"..." BUTTON

The "..." button has the options to import, export, and clean up old Suppliers