To be useful on the CPC they need:
* appropriate firmware uploaded to them (e.g. HxC or FlashFloppy)
* 5v power (an old PC power supply can be used, or you can use the monitor's 5V power output with a Y-splitter cable)
* a ribbon cable to connect it to the CPC (e.g. an old PC floppy cable which has both 3.5" and 5.25" connectors).