My younger brother magically made Mozilla's address bar "dissapear." How do I restore it!

Yesterday, my younger brother was playing around with Mozilla’s toolbar and clicked on this arrow (i have no idea which one) and somehow our damn address bar is gone.
The only things displayed on the top is the Yahoo! toolbar and the only way to go onto other sites is to look it up on Yahoo! search.
So any of you geniuses know how to restore our address bar?
Please and thank you!