You must know what is interested HD (i.e. hda1, where 'a' is first HD, and '1' is frist partition).
Create a dir in /mnt (i.e. myhd) and edit /etc/fstab in this way:
/dev/hda1 /mnt/myhd msdos defaults 0 0
Save, exit and digit: mount /mnt/myhd.
To next reboot your partition will mounted automatically.
I hope this help.