Inspect the wheels of the vehicle for bulges or wobbles. Place a lift under the front of the unit. Look for a sticker, or in the instruction manual, for the right place to set the jack. Lift up the unit.
Remove the cover from the axle with a wrench. Remove the retaining key and washers. Pull the wheel from the unit and replace. Put on the back wheels so they line up with the rear wheel hub and axle and tighten down.
Turn the mower steering wheel so the tires are facing forward. Check to ensure the steering wheel and the tires are aligned.
Remove the nut from the center of the steering wheel with the tires facing forward and lift up on the steering wheel. Align the wheel properly with the tires and push it back on. Tighten down the nut.