How to add computed attribute "Power Disconnected" a default attribute for all users/devices

Hi Anton ,
Hope you are doing great :)
I have one query please suggest me .
How can i computed attribute "Power Disconnected" a default attribute for all users/devices ?

Thanks

You can assign it to a group and add all new devices to that group.

okay Thank you
How can i add it to group ?
please suggest or share any post.