I would make quite a big fire and let the flames die down to leave a large amount of glowing wood or charcoal. The lack of insulation means that the oven won't hold it's temperature well so you have to rely on the coals/embers keeping it hot enough.
I use dried logs rather than charcoal. Build a fire with three or four logs and some kindling. You'll get a very big fire that will take the temperature off the scale, then as it begins to die down to around 400 degrees it's time to start cooking. Beware, at this temperature your pizza will cook in less than 30 seconds! I find the first one is always a dud but the second , third and fourth are perfect!
In my experience of the Pizza Oven you need a lot of charcoal (fill the container) and allow to go white when it is at its hottest. Keep the vent to chimney closed and the air vent half open to get charcoal burning, and to a quarter once glowing and turning white. Once temp. rises you can open the chimney vent to reduce any unwanted smoke, though this will add flavour to the resultant pizza. Best of luck, and fine weather.