Both CTA buttons and coupons can be edited in the same manner.
Add link - mark the text of the button/ coupon and use the hovering menu that appears to add a hyperlink.
Change color - mark the button element and go to Style Manager -> Decorations. For the field immediately around the text, choose the first option Background and pick your color from the swatch. For the rest of the button, pick a color from the Border options. If you want to make the whole button one color, just paste the color code from the one field to the other as well.
Add instructions (under the coupon) - you can edit the text below the coupon code like a regular text box, incl. effects, links and so on.
PRO TIP: Make the whole coupon code clickable by putting it in a clickable block.