Once your Group is created, you will be able to add any of your existing Senders into the custom grouping from the Groups page. In the box that says “+ Add a sender,” start typing a brand name and the associated Senders will display so that you will be able to select them and add them to the Group.
You can also add Senders to a custom Group from the main dashboard screen – just click the Groups icon (4 squares) in the Sender row and select your desired Group. Only your most frequently used Groups will display in this dropdown menu so if you don’t see what you are looking for, click “View All” to be taken to the Groups page. You also have the option to click “+ Add New” to create a new Group. Note that at this time a Sender is limited to only one custom Group at a time.