You can only create a new group when you are in connected mode.
Tap Groups.
Tap the ➕ icon in the lower-right corner.
Choose the appropriate device access type: Open, Restricted, or Closed.
Enter the title of your new group (mandatory).
Add a description under Other details (mandatory).
Select the tags you want to use for your group (Green = selected, Grey = not selected).
Tap Save to create your new group.