Nothing. Ubuntu should automatically detect the new hardware (HDD). You can format the disk using Gparted and set a permanent mount mount for your newly newly created partitions in the /etc/fstab. Do not forget to mount them on empty directories (or create some according to your need).
Originally Posted by thgthg
Use the following command to install Gparted:
After installation it can be found under System>Administration>Partition Editor menu.
sudo apt-get install gparted
Here is an excellent tutorial by Bodhi on fstab.