-The wooden thing in the bottom right is your inventory. This is where you store items that you pick up. -To pick up an item, just click it. -Once an item is in your inventory, you can use it by clicking it (which will then be indicated by a shadow appearing under it; this means you're "using" that item") and then clicking where you want to use it. -Make sure your clicking is precise. -To stop "using" an item, just click it again (which will be indicated by the shadow disappearing).
Thanks to @kimi68!
