The video below shows how to install a hard drive in the HDD Caddy. Please use the four included screws at the sides of the hard drive. These screws prevent the hard drive from moving. As last put the black plastic holder back in the HDD Caddy. When the hard drive is installed in the HDD Caddy it should be sit tight.
You can also move the bezel from the DVD or BR drive to the HDD Caddy. Please check the video below.