This is how to replace a broken toilet flush handle.
Some toilets have unique flush handles and can not be replaced with a universal flush handle. This is a basic toilet flush handle it is old and pitted and ready to break off
The nut that holds the handle on to the tank has a reversed thread, you will have to turn it clockwise to remove it.
Once you remove the nut and any washers remove them from the tank, they can cause serious problems if they go down the flush valve.
Then just pull the old handle out of the hole.
Place the new handle in to the hole place any washers and the new nut on and tighten the nut, remember the nut is a left hand thread, you will need to turn it counter clockwise to tighten it.