You can't use half a sentence to ask for a tutorial on something basic and common. Try googling your problem first. Better yet, read the forum guidelines and you'll know that you haven't provided ANY relevant information. Most people will read your thread and just ignore it.
Because I'm nice, I'll tell you how anyway.
Here's the general idea:
Go to youtube and search for 'how to install optical drive'.
Turn off the computer.
Put the drive in your computer.
Turn on your computer.
Enjoy.
If that doesn't work READ THE FORUM GUIDELINES BEFORE POSTING AGAIN.