To change the button label:
Click the button label once to select it and again to highlight the text.
When you first click the label, a blue line appears around the button. When you click the label again to highlight it, a light-blue background appears behind the text.
Type a new name.
An in-place control (shown below) appears below the button when you double-click it. If you want, select a new typeface, font style, and font size from the pop-up menus to modify the button label.