Okay, you're in the wrong category but I do have a Sonicare tooth brush. You have to unscrew the brush from the main handle. You should be able to see where the two separate just above the on/off button. Unscrew it, pull apart, and the rest should be self explanitory. The replacement brush can only go back in one way; it'll have a groove so you can't put it in bass-ackwards. Hope I helped. Good luck.