Add excerpt to grid style

I’m having trouble working out how to change the styling of the grid on the home page. I’d like to add a short excerpt (as written in the custom excerpt field on the post) below the displayed title. I can see there are different module layouts, but I can’t see where I define them for the grid. Any help greatly appreciated.

OK – I think I have it. The different modules are the blocks that you load up using Visual Composer.