|It's hard to believe you need instructions but:|
With the power cord removed, open the case, disconnect the drive's power and data cables. Sometimes the drive is in a removable bracket. In that case remove the screws holding the bracket down and then remove the bracket and drive. If the bracket isn't removable just remove the drive's retaining screws and slide it out.
For a laptop, remove the plastic case cover over the drive, remove the retaining screws, lift the drive out slightly so you can disconnect the data cable and then remove the drive.