You cast the spell, pick up some distant object with it and then fling it away. Just as you would do picking up something close, for instance,
you click and hold the mouse button then move your object and let it fly. It's actually pretty amazing what some people have posted on
YouTube - if you don't think about all the time they've spent practicing to get it working just right for the video.
I don't know how the PC version is any different however.