The Options tab has a number of design options for the Billboard component as a whole. You can change the variation of the billboard, change the background color, and add an opacity. Select the down triangle beside Color to open the full Color Panel.
In the breadcrumb above the stage, you can see that you are editing the Billboard. Double click the top text to edit.
Add text. The new text is added to the placeholder. Double click on the button label to edit the text.
Add text. The button label is changed. Select the Exit button to leave edit mode and return to the main Page content.