If you mean that the dock (bar of application icons), WAS horizontal along the bottom of the window, and now shows up VERTICALLY along the right side of the window, I think you can also move it back and forth by clicking on the line that's in the dock between the trashcan and the other items. You can click on that and drag from the side to the bottom or vice versa to change the position of the dock. You can also click and drag along the direction of the dock to make the dock bigger or smaller.