After you've already taken your PS3's Blu-ray Disc drive apart and fixed anything necessary (or maybe nothing at all), you going to have to reassemble the drive (obviously). This video teaches you how to do just that.
See the process of putting the PlayStation 3's Blu-ray drive back together after teardown. It's not too difficult, but requires patience. Verify that it works before putting the PS3 back together to save time and frustration.
Be sure to check the lens assembly for tape or other packaging before reassembling the drive fully. Some suppliers put tape or packaging on there to protect the lens.