Shortcode builder for Classic Editor is a deprecated method, that will still work, but we are no more provide support for it. Please, use the Gutenberg editor if possible.
AWB supports the Classic Editor, so you can add shortcode using this visual Shortcode builder to add backgrounds.
1. Open shortcode builder using “Advanced WordPress Backgrounds” button in editor toolbar:
2. Configure your background shortcode in popup:
3. Click “Insert” to add shortcode to your page.