How do I install this motion-sensing light switch?
You're required by law to follow the labeling and instructions.   This is not optional. 

Fortunately, your box contains both real neutral and real ground, so you can provide whatever any smart switch will require.   The switched hot is a red wire, which makes it even more straightforward.  Unfortunately your drywaller or painter painted all your wires, very sloppy, so you'll need to scrape a bit to identify colors. 

You can't put two wires on the same screw.   You would need to pull the solitary ground wire off the screw to the left, put a 6-8” pigtail ground wire n that same screw, then splice the pigtail, freed ground and smart switch grounds together.