To add another hard drive, Look at the jumper pins on the back of the new hard drive you wish to use as the secondary hard drive. Move the Jumper on those pins from MASTER to SLAVE to make the drive...
To add a new hard disk:
1) Buy a disk of a type that your diskcontroller supports
2) Shut off your computer
3) Open the computer housing and locate the cables needed to connect you hard disk...
It depends on what computer model you have. Some motherboards won't let you add a drive internally. Some cases aren't large enough or have an empty bay for a 2nd drive. The easiest, fastest, most...