I staggered this & looked everywhere to how to climb up on the cart to get to the elevator shaft and read a bunch of others that had no idea how to do it and there was no answer. The answer is to use the -shift- key, this is also -run- key but also tells her to climb up on an object such as the truck while pressing the arrow key towArds it cart to climb up on it -shift- + W forward. It usually asks to -climb- or such but doesn't & need to press -shift- to tell her to do an abnormal action as climbing. (pc keyboard version)