First you'll have become a member over at Elements Village before you can download the action.
After you down the action:
1. unzip the AA-LayerGroupTools.zip
2. in the pse 12 editor select the Expert mode
3. Go to Window>Actions
4. Use the Load Actions from the fly-out menu
5. Select both actions (mac) or select one at a time (windows)
6. in the actions panel expand the little yellow folder with the name of the action set
7. click on the name of the action and press the Play button
