Set your sewing machine to its widest zigzag stitch with a fairly long stitch length. Place the male connector (on the "in" end of your strand) at the top of the tail where it attaches to the head, with the first light right at the top edge of the fabric.

Unplug the battery and controller from the light strand. Keep it handy for testing, but don't sew while there's power running through the strand.

Zig-zag stitch back and forth over the three wires, trying not to hit any of the wires or lights with your needle. If you do hit the wires, it's likely not a big deal - the strand will still work with a couple threads running through it, but do your best to miss it and just zig-zag over the top.

Stitch the lights to the sides of the tail. I found it easiest to follow the existing seam line along the edges of the tail. Go slowly -- if you pierce one of the resin lights with your needle you could break the strand. If you do hit a light, test your strand by plugging it into the controller and battery to make sure it still lights up.

If you break one of the lights, all the ones "downstream" will go out. This can be repaired by cutting the damaged light out and re-soldering the wires to the next light in line, but this is made much harder if you have to pick out all your stitches first -- so test the strand if you hit anything.

When you reach the end of the tail, bend the lights around in a V shape (or whatever design you wish) and then sew them back up the other side. You should have a few feet of lights left over when you get back to the top. We'll attach these inside the head so it glows too.

If you want the pupils in the eyes to light up, drill a hole right in the center of each eye. I found this easier to do from the inside of the head. 

Attach the tail to the head using the included velcro, and plug in the controller, switch, and battery. 

Use a hot glue gun to arrange the rest of your light strand inside the head and mouth. I made a couple spirals inside the main cranium, then went around the lower and upper jaw just behind the teeth.

Squirt some hot glue inside each eye socket and stuff about 10 lights inside each so the eyes glow really brightly. Add a dab of hot glue on the outside to finish the pupil. On the WLED Segments page you'll learn to control just these few lights to make the eyes light up in the color of your choice.

Fix the rest of the electronics inside the head. I used strong sticky-back velcro on the battery so I can remove it for charging. I securely glued one side of the velcro to the inside of the head -- the velcro itself is often stronger than the adhesive and you want the velcro to separate (not pull both sides out) when you remove the battery.

For the switch and Sparkle Motion case, I glued them directly to the inside of the head, making sure my cords reach easily and are fairly well managed.