Wipe the entire rubber surface with alcohol to make sure it's super clean, and do the same for the back of the LED strip.
Do this on both the “outer” and “inner” faces of each shoe.
You'll need rubber bands and toothpicks to aid in glueing.
Apply a bead of adhesive to the shoe sole, starting at the inside of the heel, and stick the start of your NeoPixel strand to it.
Wrap the strip around the heel and secure with rubber bands as you go.
When you get back to where you started, use diagonal flush snips to trim the LED strip to length.
Squish a little bit of glue into the cut ends of the LED casing to create a water resistant seal, and use rubber bands to "clamp" the strip to the shoes while the glue dries, ~24 hours.