IDE1 has Master and slave, you could leave your existing HD as master, set the new one to slave.
IDE2 also has master and slave. I would set the new DVD to master and set and use existing CD-ROM as slave.
The master should be connected to the end connector and slave to the secondary connector several inches down the ribbon.
There are spare connectors for power.
It's quite straightforward. As it's your first time, spend a minute or two seeing where the secondary connectors and power plugs are.