Lighting, Light Fixtures, Ceiling and Exhaust Fans - Ground Wire?

Hi I am changing a ceiling fixture in a bedroom closet. On the fixture there is a black, white and green wire. I know the green is the ground. From the ceiling I removed a black and white from the original fixture. I can see the copper colour ground wire from the junction box is wrapped around a screw. Should I unscrew that and connect it to my green wire or leave it as us and cap off the green wire by itself? or???

Thanks

Unfasten the wire and connect it and a pigtail to the lights green wire with a wire nut. Fasten the pigtail to the box ground screw. You can also buy a wire nut with a grounding pigtail attached.

Thanks, I now have light.