There are two ways of move the Unity menu from the side to the bottom. You can either move the launcher to the bottom using a single command line statement or dconf. The best way is just to cut and paste this command into a terminal
gsettings set com.canonical.Unity.Launcher launcher-position Bottom
This setting will stay and the Unity menu with stay at the bottom even after a reboot. You can also move the menu back to the left hand side like so:
gsettings set com.canonical.Unity.Launcher launcher-position Left
Voila. You are good to go 🙂