what sciyro is saying is this:
if its not the first hd, and you have 2 hard disks, its going to be /dev/hdb.
you should make partitions on the hd and format the partitions; you will end up with /dev/hdb1,/dev/hdb2,/dev/hda3 and so on.
then you need to make a mount point (just a normal dir somewhere) and mount your hd to that point.
in example: you have formatted the 1st partition of the 2nd harddisk as reiserfs.
to mount it youll have to create a mount point, lets say we make a dir called hdb1 in your home dir.
then you can mount it using the mount command as root like "mount -t reiserfs /dev/hdb1 /home/*your username*/hdb1".
if you want to access the drive you can then just do "cd /home/*your username*/hdb1".
and btw you should edit your fstab so you wont have to mount it manually each time