IBL is in the Mental ray section. Scroll down to it and open it up. It will have a create button. Click that and you should get a yellow Environment sphere or cube appear in ya scene. Open its attribute editor and load an image for it. Then scroll down to the Emit light section, and hit tick box. Do a render and see what happens. Obviously the render times are going to depend on the usual settings, you know res etc. The results are excellent!!

Good luck

_J