In the Groups overview, click on the group.

Now click on Vehicles or Users at the top left - depending on whether you want to add a vehicle or user you want to add.

Click the + button at the top right of the group’s Vehicles or Users overview.

Place a check mark next to the vehicles or users you want to add to this group. If you want to add all vehicles or users to this group then put a check mark in the box at the top of your list.

Finally, click on Add vehicles/users to group.