Make sure the belt is position in the middle before u put the head on . hook the belt on by turning it to red. its easier when u put the height adjuster all the way up. slid the head straight onto the front. and lift the back so it goes over the ledge. and then pull the lock down to secure. amke sure the safetly switch is activated. then turn it to green. when u turn the kirby on if the green light is greena dn not off or dim or on and off. then u put the belt on correctly. if green light is not on . try again .. it comes with practise. once u get the hang of it .. its pretty easy