Typically, you load the largest (tallest head tube height) bike on the left continuing with the same sized or smaller bikes next to it, moving to the right. If bikes touch, the load order should be switched around until clearance is found between all bikes. With many different bike geometries available today, it's hard to prescribe the perect loading method for all situations. It will take a few minutes the first time, but loading will go quick as you get the hang of it.