The Four pin connector will be power
and the HDD1 and HDD2 speak for themselves.
Connect the old drive to the spare connector on the ribbon cable after making sure that you have changed the jumpers on the drive to Cable Select.
Connect the power.
Boot up and go into the BIOS. Press F12 for Boot Options and select setup or Bios or configuration. (words to that effect)
Make sure you can see the just installed drive.
Once booted, the drive "should" appear as a new letter in My Computer.
If it doesn't, take a look at Manage. Right Click My Computer and select it.
Disk Management should show the drive.