Look in your spell book, on the first tab (general or something) you should have an ability called 'shoot', drag that onto your toolbar and then you can use it to attack with your wand (which I assume you have equipped).
Edit: It works like auto attack, so press it once to start using your wand and you can stop attacking with your wand by either clicking the icon again or by moving.
Edited, Oct 19th 2007 4:50am by Tynuv