When importing recipients, you can add them into the "All Recipients" group or directly into a specific group. To create a new group, select the "New Group+" option and enter a name. If you select "+New Recipient" or "Import" while within a specific group, all new additions will be added to that group. The number listed to the right of each group name shows the amount of recipients within each group. Then, while selecting recipients for a message, you can filter recipients by group as seen below.