If your flapper needs to be replaced, it’s
probably the simplest thing you can do. All you’re going to do is flush the toilet,
let it run out- turn off the supply line first. Once you’ve drained the tank, you’re going
to simply take the old one off- it is more than likely attached to the bottom of the
refill tube, like so. Disconnect it from the handle which flushes the toilet and put the
new one in place in the reverse order, setting these little holes on the notches in the refill
tube. And then, setting the chain so that you have about an inch of slack whenever the
handle is down and the flapper is down. And that’s all there is to it.