pretty basic....remove supply line, remove the two nuts that hold the toilet to the floor flange. lift the old toilet off. clean up any wax debris from the flange. Install new wax ring, set toilet. tighten new bolts, attach supply line...flush away.
was the old toilet rocking or loose, you may need to replace the flange, or at least make sure it is SCREWED to the floor.
The rocking of the toilet is a good mention.. and if you need to shim the toilet to get it level and stop from rocking, do NOT use wooden shims. I specifically use plastic shims for this, and some have used pennies to do so. If you are replacing a toilet, measure the distance from the bottom of the tank to the floor. In some cases, the newer toilets sit higher (for comfort reasons) and the tanks are getting smaller for water savings. The reason for the measurement is that in some cases, you will need to purchase a longer supply line to reconnect the water supply to the tank. I always use teflon tape for the threads on the valve side of the supply line. In addition, when tightening the new bolts for the toilet base, be careful not to over tighten. You can crack the part where the bolt slides into the flange if you overtighten those bolts. You will probably have to cut those bolts shorter once installed if you are going to place decorative caps over them. If you are, be sure to put the plastic "bottom" before the nut so the decorative cap can "snap" into place.