Close the shut-off valve that connects to the flexible water supply line that extends from the bottom of your toilet. You should be able to do this by hand.
Flush the toilet. Remove the lid from the toilet tank. Sop up the excess water left in the tank with a towel. Ring the towel out into the toilet bowel.
Loosen with a wrench the nut that connects the flexible water supply line to the threaded valve protruding from the bottom of the toilet. Loosen the nut that connects the flexible supply line to the shut-off valve.
Wrap plumber's tape around the threaded end of the shut-off valve. Install a brass T-splitter with a pipe wrench.
Wrap plumber's tape around the female end of the flexible water supply line for the toilet bowl. Thread the hose onto one end of the T-splitter with your wrench. Tighten the other end of the water supply line onto the threaded valve protruding from the bottom of the toilet tank.
Wrap plumber's tape around the female end of the flexible water supply line of the bidet handle. Tighten the connection with the wrench.
Turn on the water supply and check all the connections for leaks. If you see any, tighten the connections with the wrench until they stop.