Dr. Brown gives Marty some 21st century clothes in order to blend in. The first of these items are shoes. Marty is surprised to see no laces. To activate them, he pushes his foot into the shoe. When his heel makes contact, the main strap constricts to hold his heel in place. Then the laces constrict to hold the ball of the heel down. Finally, the tongue of the shoe and the Nike logo glow.
Yep. Perfect. The activation is natural to the act of putting on the device. The glow acts as a status indicator and symbol. No wonder everyone wanted them.