Integration with PowerCMS is no quite available out of the box, but check out the "Database Integration Update" in your download center for PowerGallery.
Then you can use the code chunk in the PowerGallery admin (located on Add to Site > PowerStore section) and paste that into your rich text field.
The code update as specified in the "Database Integration Update" essentially translates that code behind the scenes to allow PowerGallery to work in a rich text field like the one in PowerCMS.