Method one - Use the toolbar breadcrumbs

Click on any element on the pattern.

Hover on the orange breadcrumbs

Lock them to keep them open

Select the container

Make sure the container is selected and open the sidebar

Toggle open the background layer settings tab

Toggle open the background layer settings

To change the image simply click on it or click on the replace image button

Method two - Use the toolbar document overview

Click on the pattern

Toggle open the document overview

Select the container