Short Version:
Stick the drive in, mount it to a directory, add an entry to fstab and setup the share in samba.
Long Version
Go search around the web and get yourself a few Howto's. Start with ones on Mount, fstab, and Samba.
The actual mount command will depend on the filesystem you use on the drive and its position on the IDE/SCSI chain. It will be something along the lines of:
mount -t fat32 /dev/hdc1 /mnt/otherdrive
Where 'fat32' is the filesystem '/dev/hdc1' is the drive (hdc1 is the Second Partition on the Master Drive on the second IDE channel) and '/mnt/otherdrive' is the directory you want to mount the drive to.
Go look at /etc/fstab for info on how to remount the drive on reboots.
For Samba you are best off reading the docs. There is a lot of info in there, though there are plenty of examples around of what you want to do.
Mount Info:
http://www.tldp.org/HOWTO/mini/Partition/formating.html#MOUNTINGSamba Info:
http://www.tldp.org/HOWTO/SMB-HOWTO.htmlhttp://samba.org/Adding a Second Drive:
http://www.tldp.org/LDP/LG/issue38/cooper.htmlSearch around for some more docs. There are lots out there. Hope this helps get you started.