Assuming you're using Internet Explorer:
Right click on an empty space on the Toolbar and if "Lock the toolbars" is checked, click on it to uncheck it.
Then examine the toolbar for the faint vertical lines of dots. Those are "handles" you can use to move things around. One of them is probably hiding the address bar.
To slide them around, hover the mouse cursor over one of the vertical lines until it turns into a double-headed arrow, then hold the left mouse button down and drag the "handle" (probably to the left) until the address bar appears.