Buy the toilet at your hardware or DIY store. Toilets come in all shapes, sizes and styles to match any installation. In most installations, the toilet will come in two parts: the bowl and the tank.
In addition to the toilet, you will need a few supplies to complete the installation. You will need a wax ring. This will help ensure that your toilet has an airtight seal. You will also need silicone caulk to help secure the toilet. If your toilet kit doesn't come with a fitting to connect the tank to the water supply, purchase that as well.
For a toilet replacement, after removing the toilet make sure that you clean any old wax off the toilet flange. This will help ensure a good seal. Also clean off any tile or floor underlayment beneath the toilet.
Give It a Good Seal
Turn the toilet bowl over and press the wax ring into the porcelain around the circular hole. Don't press too tight. You just want it stuck enough so that it will stay in place when you turn the bowl over. Run a thin strip of caulk along the bottom of the toilet bowl. This will give it a secure footing to the floor.
Insert the toilet bowl screws into the flange on the floor. The screws have a wide head at one end that will allow you to slip them into the flange and then adjust them in the flange channel. The two screws should be directly opposite each other and should line up with the holes in the toilet bowl.
Securing the Toilet
Turn the toilet bowl over so the wax ring is now facing the floor. It's helpful to get a friend to assist you at this point. Gently lower the bowl to the toilet flange, making sure that the two screws poke up through the holes in the base of the toilet bowl. When the two screws are aligned properly, press the toilet bowl firmly down on the floor, ensuring a good seal with the wax ring.
Tighten the Screws
Screw the nuts onto the top of the screws. At first, tighten them just by hand, then gently with a wrench . Do one side and then the other. Do not overtighten, because this might crack the bowl. You can cut off the excess bit of screw with a hacksaw. Place the screw caps on top of the screws.
Secure the Tank
Set the tank on top of the toilet. It will sit into a recess at the back of the bowl. Align the flapper hole at the bottom of the tank with the access hole at the top of the bowl. Tighten this down with the screws provided through the tank. Again, do this first by hand, then gently with a wrench.
Attach the plumbing fitting from the tank to the water supply. The end attached to the tank can be tightened by hand, while the end running into the wall will need to be tightened with a wrench.
Caulk again at the bottom of the toilet. Allow this to dry for an hour.
Turn on the water supply and test the toilet. Check for leaks. Install a toilet seat if it did not come included in your kit.