Cook times for steaming brown rice vary by steamer, so it is always best to check the manufacturer's booklet supplied with the appliance. In general, however, steam brown rice for 65 to 70 minutes.
It is typically a good idea to rinse and soak rice before steaming. Place the rice in a dish, and fill it with enough water to just barely cover it. Let the rice sit for around two hours and strain the water out before placing in the steamer. Be sure to check the manufacturer's instructions for how much water to use when steaming, and be sure to use the right basket attachment.