I dont know about the zombies going on those objects but to create fire you need to use the FX Browser this video does a good job at showing you how use it
https://www.youtube.com/watch?v=tp5KX1hstiI
He also has some other great tuto...

The past two times i've tried to make a enclosed space, it ends up looking like this. https://gyazo.com/e765604d1a30b48f4667f0edfea71311
It is as if it has a low opacity since you can kinda see through it.
https://gyazo.com/e6242a859d808c79742c0bb560d3e4f6