Lift the mower deck up to its highest position via the deck's lift lever, located on the rear fender. This gives you room to work under the mower deck.
Place a wrench on the bolt that runs through the center of the mower deck's wheel. Locate the nut on the other end of the bolt and place a wrench on it.
Rotate the wrench on the bolt counterclockwise until the nut comes off the bolt.
Push the bolt out of the mounting bracket on the mower deck. If the bolt sticks, tap it loose with a mallet.
Slide the bolt through the hole in the center of the replacement wheel and then slide the bolt through the mounting bracket on the mower deck.
Thread the nut onto the end of the bolt as far as you can with your fingers. This will help to prevent cross-threading the bolt and nut.
Place a wrench on the bolt head and the nut and tighten the bolt and nut with the wrenches.