It’s probaly quite straight away, and thus if feel stupid asking this but were do I turn on AO???
World buttons.
That’s right, it’s in world buttons. If I could elaborate in case you still can’t find it or there are newbies not familiar with the software. Go to the shading section (F5), click on the world icon called world buttons. In here, there is a panel with 2 tabs mist/stars/physics and amb occ above it. Click on amb occ, then hit the button called Ambient Occlusion.
I don’t really use AO that much because it seems to take ages. I did one render with it and the results didn’t seem much better than with my own light setup. I guess I’ll have to play about with it a bit more - I’ve heard good things about it.