I'm talking about the planets on the skybox, like the moon or the sun. I kinda need another planet besides those 2. Is there a way?
example: https://prnt.sc/10tvv7q
I am not exactly sure what you're asking for but I think your asking for worlds? You can do that by adding mutiple places to your game!
Help: https://developer.roblox.com/en-us/articles/games-and-places
You cannot add another moon or sun. You can however remove them by the CelestialBodiesShown
property.
The sky is actually fake - it's an illusion created by piecing together other images and is called a skybox. If you instead want to change that, look here