The phrase "___ kicks ass!" means that something is really great. You use it like this:
Have you played Call Of Fury 3 yet? It kicks ass!
This phrase is very casual. It's used more by younger people and less by older people.
You use "___ kicks ass" to talk about things that are great in a kind of aggressive way. So use it when talking about things like
- video games
- sports teams
It would be a little unusual to tell someone that, for example, their flower garden "kicks ass".