Ring 2 Standard Electrical Box Install

I have a Ring 2 to replace my current wired doorbell. I have concrete walls with a stucco finish. The current opening in the wall is a standard single electrical gang box with the single screw at the top and bottom. There's currently a standard cover plate screwed to the box and the doorbell is screwed to the cover plate itself. How do I go about mounting the Ring 2 to a standard electrical gang box opening? Thanks.