Begin by preparing your workspace. Lay an old towel on the floor around the base of the toilet to catch any water drips. Locate the water supply shut-off valve, typically on the wall behind the toilet (an oval or football-shaped handle). Turn the valve clockwise until it stops to shut off the water supply. Next, flush the toilet and hold the flush handle down to drain as much water as possible from the tank. You can use a small bucket to catch any water from the supply line in later steps.

Locate the caps covering the toilet seat bolts at the back of the toilet bowl. Use a flathead screwdriver to gently pry these caps open. Underneath, you will find the heads of the bolts. From under the toilet bowl rim, locate the plastic or metal nuts holding these bolts in place. Use a screwdriver to hold the bolt head steady while you unscrew the nuts by hand or with a pair of pliers. Once the nuts are removed, lift the old toilet seat and lid straight up and off the bowl. This is a good opportunity to thoroughly clean the surface of the toilet bowl where the old seat was mounted using a cleaning rag and an all-purpose cleaner.

Unpack the bidet's mounting hardware. Place the mounting plate over the two bolt holes on the back of the toilet bowl. Insert the square guide rails into the mounting plate and then slide the mounting bolts through the guides and the holes in the toilet bowl. From underneath, thread the nuts onto the bolts and hand-tighten them so the plate is snug but can still be moved slightly for adjustment.

Align the bidet toilet seat with the mounting plate that you just installed. Gently slide the seat backward along the plate until you hear and feel a solid 'click'. This sound confirms that the seat is securely locked onto the bracket. Now, check the seat's alignment with the front of the toilet bowl. Adjust as needed by slightly loosening the nuts, shifting the seat and plate together, and then re-tightening the nuts securely from underneath with a screwdriver.

With the water off, place your bucket or towel directly under the connection point where the flexible water supply hose meets the bottom of the toilet tank. Using an adjustable wrench or channel-lock pliers, grip the coupling nut on the supply hose and turn it counter-clockwise to loosen and disconnect it from the tank's fill valve. A small amount of water will drain from the hose and tank, so be prepared.

Take the T-valve that was included with your bidet seat. Inspect it to ensure the black rubber cone washer is correctly seated inside the top female-threaded connection. Carefully thread the T-valve by hand onto the male-threaded fill valve at the bottom of the toilet tank. Once it's hand-tight, use your adjustable wrench to give it an additional quarter-turn to create a snug, leak-proof seal. Do not overtighten.

You will now connect two hoses to the new T-valve. First, take the original flexible water supply hose (coming from the wall valve) and connect it to the bottom male-threaded connection of the T-valve. Hand-tighten, then snug with a wrench. Second, take the new, smaller bidet hose supplied with the kit. Connect one end to the side outlet of the T-valve and the other end to the water inlet port on the bidet seat itself. All these connections should be hand-tightened first, then given a gentle quarter-turn with the wrench.

Turn the water supply shut-off valve at the wall counter-clockwise very slowly. This prevents a sudden pressure surge, known as water hammer. Listen for the sound of the toilet tank refilling. As it fills, carefully inspect all three connections on and around the T-valve for any signs of moisture or drips. Use a dry paper towel and wipe each connection point; the paper will make even the smallest leak immediately obvious. If all connections are dry, plug the bidet's power cord into the GFCI outlet. The bidet will likely make a sound as it initializes. Test the functions using the remote control or side panel.