Unwind the rope lights so that they lay flat.
Lay the rope along the ground so that it follows the length of the railing. The rope should start at one end of the railing and continue to the other end. If you are using an outdoors extension cord, start the rope at the railing, if you are not, start the rope at the electrical outlet. You may need to attach multiple rope lights together, by plugging them into each other, to reach the full distance.
Start at the end that is closest to the electrical outlet, whether it is the top or bottom part of the railing.
Wind all of the rope lighting back up toward you.
Start at the top side of the railing and pass the rope through the railing. Wind the rope around the railing so that it winds over and under the railing.
Continue to wrap the rope lights around from one end of the railing toward the other.
Stop once you have reached the end of the railing. You may tuck the rope's end under a section of the wrapped rope or you can insert a hook or clap into your railing that will hold the rope into place at the end.