The 3.5" Drive will still need to be connected with a standard 5V / 12V supply as usual and you will need to have modified it to send a ready signal. Additionally, PC drives are usually configured to be Drive B: (DS1), so the drive will also be seen as drive B: by the CPC. However, this can also usually be configured inside the floppy, so that the drive will function as drive A: on the CPC.
== Links ==
[http://www.pitsch.de/stuff/amiga/floppy.htm| Enabling the Ready Signal] - German Site with instructions and photos of how to enable the ready signal for many common floppy drives.