I've never put a lot of effort into learning to throat sing, but from what I hear it's very similar to playing a didgeridoo, which I do play. I'd assume that you're going to want to push air out using your diaphragm. Once you're doing that, you can use your mouth and your tongue to change the resonant frequencies of the air. I'm not entirely sure what this will sound like, since I use a meter long wooden tube and not just my diaphragm and mouth, but you should be able to pick up changes in frequencies, and manipulate them from there.

On an unrelated note, is it possible to circular breath while throat singing?