Turn the key in the cyl untill the key is horizonal or straight across . Notice the little round pin on the top of the cyl towards the key end , it should push down flush with the outer edge of the cyl then you can install it in the handle . When its installed turn the key and the pin should raise up into the small hole in the handle to lock it in place. To remove it from the handle, turn the key in the horizonal position and take a peice of stiff wire with a 90 degree bend on the end and insert it in the small hole in the handle and push the pin in and the cyl should slide out. Is the cyl you purchased an original ?