How can I add a banner about sale or promotion?

To quickly create a promotional content block use Call to action block. This allows you to quickly draw attention to your sale, event, promotion, or another action. You don't even need to use an image editor. Here's how to add a responsive banner area to your page:

1. Choose a place where you want to add your promo banner and click + Add block button. 

2. In the Blocks Library, choose Call to action block with one or two buttons and image background.

3. Customize the block title and subtitle with the information about your sale or promotion. For maximum impact, consider disabling block subtitle in Block Settings.

4. Customize the block background with a promotional image. 

5. Click Publish to make your banner live.

For more details and ideas on how to customize the Call to action block visit this tutorial.