Hi Dan,
To connect Solutions to Solutions Category, you need to install MB Relationships extension. And then follow the extension docs. Basically, all you need is the following code in functions.php:
add_action( 'mb_relationships_init', function() {
MB_Relationships_API::register( array(
'id' => 'solutions_to_solution_categories',
'from' => 'solution',
'to' => 'solution_category',
) );
} );
Then you can select connected solution categories when you edit a solution.
To get the connected solution categories to show on the frontend, I think it's hard to do in BB, since it doesn't support to make custom query with custom arguments yet :(. The way you query related posts is described here.
