It's a press fit and a tight one. I've used two different methods over the years. One is to wedge your knees under the wheel and put a lot of upward (toward your chest) force on the wheel while striking the end of the shaft with a hammer (put the nut on the shaft to where the edge of the nut and end of the shaft are equal so you don't bugger the threads on the shaft). A couple of stout raps with the hammer should pop the wheel off. Method two, and the only one I use now that I'm old and inflexible, is to use a universal puller,
Like this one., except using large "J" hooks from the hardware store in place of the bolts. Place the hook part of the J bolts around the spokes of the steering wheel. Put the shaft of the puller against the steering mast and get it pretty tight, a stout pull. Once you're to the point where you feel it's about to break something give the end of the puller shaft a good rap with a hammer and the wheel will pop loose.