The primary group you are working on is screen-based. When you add new objects or edit the playlist, it is already assigned to the corresponding group of screens. So there’s no need to perform any extra actions to send a playlist to screens; it will be set automatically.
To check what screens are assigned to play content from the playlist, you can switch to the Screens section of the playlist here:
If you wish to move a screen to any other group, you can refer to the Screens section on the left side list and move the screen across Groups:
Choosing the new group:
And that’s it!