The hard drives usually comes with direction, but basically there is a little plastic thin when you have to place in one of the pins where it conects to make it a master or slave. Basically you pull out the plastic peice and put it in the situation where it is consider the master and then your 2nd one to be consider the slave. I wish i had a picture to show you.
Step 1:
Decide which hard drive will be the startup (master) drive. If this drive was the startup drive previously, or if it's a new hard drive, then the master drive designation will already be set.
Step 2:
To change the designation of a new drive to be a slave drive, skip to step 4.
Step 3:
To change the designation of an existing drive to be a slave drive: Turn off the computer, unplug the power cord, remove the drive from its drive bay, and disconnect the drive from its power cord and ribbon cable.
Step 4:
Check the hard drive documentation or the label on the drive itself for master/slave jumper settings.
Step 5:
Find the jumpers on the circuit board of the drive. Jumpers are plastic plugs with metal sleeves that form a circuit between a pair of pins. Jumper locations are labeled on the board with a J followed by a number (such as J20).
Step 6:
Use tweezers or very small pliers to remove or reposition the jumpers to the configuration shown in the documentation or on the disk label.