Park the RV at a level location. Turn off the water connection at the campsite. Turn off the internal water pump. Flush the toilet to remove any water from the system.
Use the adjustable wrench to loosen the water connection at the back of the toilet. Use the towel if any water leaked from this connection.
Use the adjustable wrench to loosen the nuts from the bolts that extend into the base of the toilet and hold it in place. Remove the nuts.
Lift up the toilet and place it on its side. Looking down on the bathroom floor, you will see a round flange. Inside this flange is a rubber seal. Lift up the rubber toilet seal with your hand and discard. If the rubber toilet seal is not in the flange, it will be stuck to the base of the toilet. Remove it in the same manner and discard it.
Take the new seal out of its package and place it on the top of the flange.
Place the toilet onto the bolts and tighten the nuts. Reconnect the water to the back of the toilet. Turn on the water to the RV and turn on the water pump. Flush the toilet and check for leaks. If there are leaks, retighten the nuts.