How do I set bidding adjustment for Ad group level?

This is the action you need to set if you wish to adjust your bidding for ad group level in an automated way

Set, decrease, or increase Max. CPC

From the Ad Groups tab, this action exists under the Max. CPC column:

Select your desired action:

You can set an Upper Max. CPC limit, and condition by performance metrics. Any default data or data you have chosen to export from Google ads will be displayed.

After saving the rule, all ad groups that will be affected from it, will turn to bold.

In order to execute the rule, go to Export icon (after saving the view):