"Toilet pan" is a term used mostly in the U.K. and Europe for the part of the toilet that is normally called the bowl in the United States. The major difference between the two types of fixtures is that the toilet pan generally has its waste outlet located at the rear, rather than underneath. Connecting toilet pan fittings is generally a little bit easier than with toilet bowls, mostly because you don't have to deal with any messy wax rings.
Insert the pan connector into the waste pipe on the wall. Make sure that the connector fits snugly.
Place the cistern on top of the toilet pan. Insert the cistern bolts through the bottom of the cistern and secure them with the nuts from below.
Move the toilet pan and cistern in place against the wall. As you do so, slip the waste pipe on the back of the toilet pan into the connector collar.
Use the level to check that the toilet is even. Slip plastic or wooden shims underneath the pan base to bring it up to level.
Using a pencil, make a mark around the base of the pan. Also make marks through the holes in the base of the pan and the back of the cistern. Pull the toilet pan and cistern out of the way.
Insert the silicone caulk in the caulk gun. Trim off the end of the gun at a 45-degree angle. Squeeze the trigger on the gun and apply a bead of silicone on the inside of the pencil outline.
Replace the toilet pan. Slip the waste line at the back of the pan into the waste collar. Press the toilet pan down to help distribute the silicone caulk.
Use a power drill to drill the screws into the base of the pan and the back of the cistern.