A secondary hard drive (fat32, ntfs, etc) can be added for additional storage in your Amahi HDA.
First thing's first, make sure your drive is formatted properlydetected by the BIOS, connected properly and detected by formatted properly. Once the biosBIOS sees it, you need to have it partitioned. You can check this with the following command (run before and after connecting the (USB)disk):
dmesg
http://www.mjmwired.net/resources/mjm-fedora-f9.html
== Partitioning a Brand New Disk==
If you have a blank, unpartitioned, drive, you have to 1) partition it and 2) format it.
If you want to move this disk to windows machines, you may want to format it as NTFS. To do this, it's best if you do that in Windows.
To make a partition, it's best to use (as root)
gparted
in your fedora desktop, as it's graphical and will help make decisions.