The best method is to place a towel down on a flat surface to prevent damaging the face of the watch. Place the watch face down, slide the pin through the hole in the strap and align it so you can put one end into the hole on one side or the other. If you have help it is easier for sure, but hold the watch with one hand and the strap with the other, then use a small screwdriver to compress the spring bar enough to get it under the edge of the watch. Push the strap toward the center of the watch while also using the screwdriver or spring bar tool to push the spring bar toward the center of the watch until it snaps into the hole. Once it is in on both sides use the screwdriver or spring bar tool to make sure that both sides of the spring bar are fully extended toward the outside of the watch so they are completely engaged in the hole. If you are still having trouble you can always go to a jeweler or watch counter at the retail store and they can often help you with their repair tools.