The Insert tab on the Structure panel is where everything starts in the Instant Builder. From there you can add:
You can see the hierarchy of the Elements on the active page in the Visual Canvas on the Layers tab.
Insert a Section or Element on a page
In the Builder, open the Insert tab.
Find the Section or Element you want to add to your page.
Switch the selector at the top to go from viewing Sections to Elements or vice versa.
Drag it onto the page.