Pushing the handle down on your toilet initiates a series of events inside the toilet's tank. These events allow water to flow to and from the tank. The chain inside the tank connects the handle assembly to the flapper, while the flapper controls the flow of water from the tank. Without the chain, the command to flush never reaches the flapper. Replacing, and properly adjusting, a missing or broken chain restores your toilet's ability to flush.
Turn the water stop valve, behind the toilet, all the way clockwise to stop the flow of water to the toilet.
Remove the tank lid. Reach down into the tank and raise the flapper by hand. Allow all water inside the tank to drain. If you wish, wear a rubber dishwashing glove to prevent your hand from getting wet.
Locate the narrow strip of plastic or metal on the backside of the toilet handle. This lever contains three eyelets that allow for attachment of the chain. Select the hole directly above the flapper.
Hold the hook at the end of the chain against the hole, and allow the chain to fall straight down. Observe where the other end of the chain meets the flapper. Once attached to the flapper, the chain should be able to hang straight down with only 1/2 inch of slack. If necessary, use needle nose pliers to remove a section of links to customize the chain to proper length.
Hook the chain into the proper eyelet on the flush handle. Hook the other end to the eyelet or lip near the front of the flapper.
Open the water stop valve. Allow the tank to refill, before replacing the lid.