How can I move the panel from the top to the bottom?

(Assuming you're using the Classic desktop) you can just Super-Alt-Drag the panels.

If you're using Unity, you can't customise this. If it's something you need, I'd strongly suggest trying the classic desktop.

Simple answer: You can't. At least not with Unity.

More complicated answer: Unity Desktop(and Gnome Shell) is made to be simple and look the same on every computer. If you want something that is more customisable, try for example KDE or XFCE, which you can install through the software centre. Then you can set the desktop environment you want to use from the login screen.

Regarding moving the panel in Unity: comment #2 in Movement of Unity launcher has this:

I think the report actually meant that the launcher should be movable to other edges of the screen. I'm afraid that won't work with our broader design goals, so we won't implement that. We want the launcher always close to the Ubuntu button.

status wontfix

Mark

AFAIK, that's how it still is.

"Super+Alt+Right-click" on the top panel and select "properties".

Choose "Orientation" from it.

You cannot move the panel from the top to the bottom using the default Unity desktop.

If you install gnome-shell from Ubuntu Software Centre and use gnome classic desktop (by selecting it from the login menu) then you can move the panel as described in the other answers.