Tom,
There should be a small lever on the right rear of the tranny tunnel in front of the seat. Push down, I think, on the lever and that will push down on the manual hydro release valves so you can safely push the Cub around. You shouldn't do this very far or very fast.
Go here for the pdf manuals for you new Cub Cadet:
72-125 Ops Manual
72-125 Service Manual
BTW, I really like the looks of them zig zag flat fenders!