If you chose Assign to Groups, the Assign "your application name" to Groups pop up will be appeared.
- Click the Assign button If you want to assign Groups.
In the Search field, you can search for exact Groups.
- Click the Done.
At the end of the assigning groups process, you will be able to spot assigned groups.
- Click
If you want to edit groups or click 
If you want to unassign groups. Unassigning Group pop up will appear.
- Click OK for the unassigning group.