Remove the plastic positioner from the optical bay hard drive enclosure by pressing in on one of the clips on either side and lifting it up and out of the enclosure.

Make sure that the hard drive connectors are facing down before placing it into the enclosure.

Gently place the hard drive into the enclosure's hard drive slot.

While firmly holding the enclosure in place with one hand, use your other hand to press the hard drive into the enclosure connectors.

Once the hard drive is snug, reinsert the plastic positioner while holding the hard drive against the bottom of the enclosure.

Reconnect any cables you have removed from the original optical drive onto the optical bay enclosure.