A. Generally, with most toilets: Turn off the water supply and flush the toilet. Reach in and unhook the ears of the flapper and unhook the chain from the trip lever. Install an identical flapper to the original that came from the factory. Do expect to get your hands dirty from the old flapper. Simply reinstall the new one in reverse order. Note that should you have very old brass pipes inside of your toilet, be careful not to be rough on them. They can easily break and end up leaking. After you have replaced your flapper, and the toilet tank bowl has refilled, the water fill valve should not leak (be going on and off in cycles). If it does, then we recommend putting some food coloring into your tank. This can help diagnose the problem. The colored water should not be going into the bowl (unless you flush the toilet of course). If the food color does go into the bowl, then possibly the flapper is not the correct one, the surface where the toilet flapper sits has eroded (feel below where the flapper touched the toilet and see if you can feel erosion/groove), or you may only need to add some slack to the chain.