It's very easy. Make sure your dough isn't sticky at all, and coat it with a layer of olive oil. Then place it directly on the grill for a few minutes (until the top starts to look puffy and the bottom seems done - bad description, sorry). Flip it, add your toppings and put the lid down until it's as done as you like. I usually stop when the dough seems firm and the cheese is all melted. Make sure your toppings are fully cooked as they won't be on the grill long enough to cook.
I haven't done this yet this year, but have pizza on the menu for Wed, so might cook it this way for a change! Great idea!