You can use the Linux /etc/fstab to automatically mount hard drives on system boot up.  In the file you should see all your default system mount points, to add another hard drive or mount point, just create a new line at the bottom of the file and put in the following info

/dev/drive          /mount/point    filesystem   options    0      0

Example:

/dev/sdb1           /mnt/    ext4       rw,defaults         0      0

You can also use the UUID of the drive. You can find the UUID by running the following command

sudo blkid

In the fstab file just replace the /dev/drivename with the UUID

UUID=ba84c923-4413-090a-441d-6e12f32991b3         /mnt    ext4  rw   0      0