Step 1: upload your banner and open it in the Ad Editor
Step 2: Go to the "Elements" section and click on "20%OFF" (discount code widget) in Ad Editor
That is it - now you can configure colors and other settings:
How will it work?
If you use a discount code element in a banner, then after visitor will close this banner, he will still be able to see the discount code in a small Ribbon at the bottom area of the site.
In case you also decide to use a countdown timer, then after closing the banner, the small Ribbon will show both the discount code and also the time left to use it. Example below:
And here you can see how the Ribbon would look like with and without the countdown timer: