Trying to use Menu with main menu on the left, 2nd on the top, content to the right

I'm trying to setup a menu system with Divi Ultimate Header where the primary menu is down the left side, the secondary menu is across the top, and the content loads in to the right of the main vertical navigation, like the attached mockup.

Currently, I can get the vertical main nav and horizontal secondary nav how I want them, but the content loads below the bottom of the vertical navigation, not beside it.

Any ideas as to how I can get this to work? Thanks in advance!