Hello! I think my graveyard needs a big, scary full moon that will glow brightly in the sky, illuminating some areas while making others even darker. Only problem is I have no idea how to add a moon to my map, and I also don't want to change the sky I already have. Any suggestions?

Um....you could add a second sun flare. Or rather, a bouncing light. Just scale it down and change its color (I describe how to change the color/size of the sun effect HERE)
Beyond that the game supports a maximum of 2 directional lights, if you wanted your moon to cast shadows. Otherwise you could fiddle with the spot/omni lights which at the moment I am not familiar with. As for the bouncing light, look at tatooine as an example, I havent tried setting one up myself. Hope this helps!

Take the Yavin skydome object(yav_sky_planet), retexture it(remember you're dealing with transparency), add it to your map.

Then add a directional light as well.

Yes that did it! Thanks guys helped a ton