If you're looking at the back of the brush handle and brush head (as shown in the graphic above), you'll also see an embossed arrow on the metal part of the brush handle and a small embossed notch on the back of the brush head—you can slip the brush head on with these two marks lined up, then slightly twist the brush head clockwise until it locks into place.

To install the brush head with the brush head and the charging indicator light facing you, place the brush head over the tip of the wand until it stops, then while gently pulling the brush head down, turn the brush head slightly counter-clockwise until it clicks down, and then turn clockwise to lock.

To remove the brush head, with the brush head and the charging indicator light facing you, hold the wand and turn the brush head slightly counter-clockwise until it stops, then lift up to remove the brush head.