If your amiga HD is an ide device, attach it and it (use a spare IDE channel if possible and opt for cable select) and should become visible from WinUAE's "add harddrive" option in the drives section of the interface.
Don't attempt to access the drive from windows itself, it'll probably want to format it.
I've mounted real amiga hard drives on UAE many times when I've needed to transfer data too big for disks and when I was out of CDs. Also especially handy for reading large amounts of data, for backup purposes.
Nowadays, though, I just use a LAN.
