You can remove the axles or leave them in place. I've done it both ways but if it were me, I'd remove the axles first...it makes the thing a bit more manageable.
I hope that you also acquired the shims that were originally with that pumpkin. Read up:
One shim,
two shim,
red shim,
blue shim.
You'll need a floor jack to lower and lift the pumpkin into place. You should fabricate some sort of holding fixture to mount on the jack so the punkin doesn't fall off on your noggin.
An auto tranny jack with appropriately located wood chocks to hold the pumpkin might be one way to do this also.
The holes in the subframe for the pumpkin are located so precisely that the pumpkin has to be EXACTLY perpendicular to the subframe for the studs to slide through the holes. There is ZERO 'slop' to wiggle it in place.