I was able to spawn the Skydome.
I tried to use the bodygroup tool on them but nothing. It doesn't even select it. Or if it does select it, then it show nothing. How do I change the Skydome and most importantly, how do I remove it after placing it because not only I can't change it, but I can't seem to be able to remove it too.

tl;dr: How to make it work with the Bodygroup tool & how to remove it.