First you partition it using fdisk, then format it with mke2fs (for EXT3 use the -j switch on mke2fs), then you can add it to your /etc/fstab and mount it.
If you want a nice graphical interface you can use Webmin's partition manager and disk and network file systems modules. You can get Webmin from
http://www.webmin.com
Webmin's partition manager is under hardware/partition manager
The file system module is System/Disk and Network Filesystems