Trebuchet not loading

So, i was able to build a complete trebuchet, put 100% counterweight in it, put 10 Stonethingies to shoot with in it, and now im supposed to WALK against the reload button? That does absolutely nothing. Is there a trick here?

  1. Use the arms on either side to aim it.
  2. Use ‘E’ to pull the leaver to fire it.
  3. Use ‘E’ on the reel to put it back in the firing position.

Actually, what you have to do is put one of those stones into the firing slot in the inventory window! This is similar to when you have a furnace running with coal, there is only 1 coal “loaded” at a time and it appears at the top of the inventory window.