With a Conditional Layout, the last thing you need to do is to set the conditions of the layout. This is best done last, because as soon as you set the conditions, the layout is active, and if you do this after creating the Layout Sections, but before editing them, the pages displayed that fit the conditions would be empty in those sections.
To add a condition, or conditions, simply mouse over the bottom of the Layout, and choose Add A Condition. This brings up the Layout Conditions Dialog, as seen below. Please see Understanding Conditional Layouts for more information on Conditional Layouts, but for this example, as we want this layout to display on Single Posts, we just need to go to Posts and select the All Posts condition.