The first step to removing your old toilet is to ensure that you have turned off the water access to the unit. The water shutoff valve is located at the back base of the toilet and is usually a silver cable with a knob attached to it. To ensure the water has been shutoff properly you should flush the toilet, the water in the tank and the bowl should remain empty. Next you are going to the water supply cord from the toilet by unscrewing it from the base of the toilet. Now you will need to unscrew the bottom of the base from the floor using a wrench, if the bolts have rusted over due to water exposure and you are unable to move the bolts you may need to cut the bolts off using a saw. Before you move on to attaching the new toilet you should clean the surface area.