Some of these twist off very nicely but most don't. Mine are held into the ceiling with 2 spring clips. Just get your fingers under the edge of the light between the ceiling and the light (you may need a plastic putty knive to help you get started). Then pull straight down (you have to pull pretty hard) until the light pops out of the mounting hole (reverse the process to reinstall the lights). Using work gloves, grip the body of the light with one hand and the lens with the other and twist counter clock wise.
Some are so difficult that even this method won't work. Look at the body sides carefully and you will see 2 flat springs (180 apart) each holding a plastic button into the body. Remove the spring and pry out the plastic botton. You can then lift out the glass lense. I have never successfully reinstalled the flat springs so I stick the lenses back in place with 3M wall hanging putty. I have never had a lens secured with this putty fall out going down the road.
