hmm.. ok well first you have to be able to open your computer case to take out the old drive to install the new drive in it's place. Here is a page to read to help you more.
Read the part about how to remove the case screws
There it tells you about opening your case then jump to the second link provided
Installing a CD/DVD Drive
The last part : Guide to Installing IDE/ATA devices
I could try to give tutorial but I would probably confuse you more those links should help you better.