The engine does have oil in it although its only in the gearbox and clutch case, there will be a drain plug underneath, warm the engine before attempting to drain it. Before you do drain it find out how much to put back in, there is usually a dipstick or a window in the clutch case to use as a level, you need to have the bike vertical when filling to the correct level, as Mikey said, the other oil is two stroke oil and your engine burns this so you need to keep it topped up, although there should be a warning light when its getting low.