You may have to remove an existing toilet. Before you start, turn off the water supply at the shut-off value where the water supply line is connected. After you turn off the water, flush the toilet to get as much of the water out of the system as possible. Use a small container of some sort to scoop the excess water from the tank and bowl. Disconnect the water line. Keep some rags nearby so that you can wipe up any water.
Use your pliers to hold the nuts as you remove the two screws from inside the tank. Remove the nuts from the two or three toilet bolts securing the bowl to the floor. Use a slight twisting motion to loosen the wax ring underneath the toilet. Pull up on the toilet bowl to remove it.
The floor must be structurally sound. Examine the floor area for any signs of damaged or weakness in the subfloor as well as the joists. Make repairs if necessary.
Turn the bowl upside down on a piece of cloth or rug. This will help avoid scratching the porcelain. Apply the wax ring to the bowl opening. If the wax ring has a horn, inset it into the toilet flange in the floor. Apply slight pressure to the wax ring so that it adheres to the bowl and won't fall off when you turn the bowl over.
Set the toilets bolts into place. Apply some bathroom caulk around the perimeter of the area where the bowl rest on the floor. Lift the bowl and position the bolt openings over the floor bolts. Lower the bowl into place. Use a slight turning motion to seal the bowl. If the bolts are too long,use a hacksaw to cut them to the appropriate length. Put the washer and nuts on the bolts. Exercise extreme care as you tighten the bolts to prevent cracking the porcelain.
To attach the tank to the bowl, line up the seat in the middle of the tank with the hole in the bowl. Make sure that you put the gasket around the connection on the exterior bottom of the tank. The tank must be level as you tighten the tank to the bowl. Connect the water supply line to the inlet on the bottom of the tank. Connect the supply line to the shut off valve. Fill the tank with water and check for leaks.