you can just poke the new one in and BIOS will detect it (if not, you will have to make it auto-detect).
You might need to set the old one to "Master" if not already done
Look at the label on the disk, and any instructions provided on how to connect and set jumpers.
the Master has to go at the end of the IDE ribbon cable (you will find the cable has two connectors on it, one at the end and one in the middle
(I think)
But if you are already using a CD or DVD drive on the other connector, you will need another cable
Unless you have avery old version of Windows, it will recognise what drive you have.
If Windows doe not automatically find it, you can tinker with Disk Manager but this is very tiresome. Post back if this happens.