Start with a new blank image, make your own size, but roughly about 60 by 60 pixels. Select the Preset shapes tool .  Then select a button from the Tool options menu.

Make it any color you like. Insert some text if you wish by selecting the text tool .

Place the text symbol onto the button and left click, you will then be presented with the text menu.

Enter your text into the text box select your color, test size and style and click OK.

Position your test into the button not too close to the edges as it will not be displayed. And that is it, now just save the button