The Contents pane is a tree structure that shows the hierarchical layout of your content in terms of the elements on the page or Popup - you'll see all the objects in your content nested within sections and boxes.
To access your Contents pane click the small arrow at the far left, or the Contents button at the bottom of the Unbounce Builder.
Click an item in the Contents to select it within your content. You can rename objects by double-clicking them.
Click the arrow on the right of the Contents section to close the pane.