Click inside the applet and then use the arrow keys to control the wizard. Use "Tab" to scroll through your inventory, "d" to drop the current item and "SPACE" to use it.

Here are a couple hints on the spells you can do... Pay attention to the order.

Sorbum Granus (Extra Health) - Henbane & Slippery Elm
Treorbum Tanis (Full Health) - Henbane, Poppy & Slippery Elm
Fugit Vim (Freeze Moving Ent) -
Caldus Divum (Kill Bat) -
Raniam Vim (Kill Ghost) -
Beezaltium (Kill Demon) -
Ticum Deum (Kill Devil) -
Popus Lupis (Kill Death) -
Natum Tan (Destroy Tree) -
Frenis Vim (Destroy Wall) -
Voidum (Create Black Hole) -
Asi Tacil (Create Temporal Fix) -
Fugor Arbum (Create Tree) -
Ad Argum (Create Wall) -