Their patent states that the LEDs should be placed on exposed skin. That's the area that they have tested. Light scatters or diffuses in the hair, so the areas that you're exposing to LEDs to might need to be shaved a little.

Per the article, "It will be appreciated that the apparatus of the invention can be used to direct light to via the transcutaneous transosseous route of the skull but that areas of the skull substantially bereft of hair, such as the forehead/frontal lobes and/or temple regions are the preferred sites to receive light because the presence of hair can reduce and/or scatter the light and effect the power intensity at the treatment site. "