...
Select a Group that contains (most of) the devices the devices you wish to edit. Don't worry if the Group doesn't contain every device you need to edit - you can always repeat the process on another Group. It's simply faster to select a Group that contains as many devices that you wish to edit as possible as the process can be performed potentially only a single time.
You will need Admin level access on the Group to edit the devices.
...
Once you have your attributes set as desired, scroll to the bottom of the page and click Submit.
You can also see at the bottom of the page a table showing the devices the changes will be applied to.
...