So I've found several weapon mods that sound pretty awesome, like a scope for my SMG, and improvements for my Shotgun.
And I've found a 'Weapon Bench' which, when I go to alter my loadout, also has a convenient 'modify' button that shows me two empty mod slots on all of my shiny new guns. I can inspect the 3D model of a given weapon more closely, and at multiple angles, all very nice.
But I cannot, for the life of me, figure out how to attach one of these shiny, awesome mods, to my shiny deadly guns. I see two 'slots', one of which is lit up in red as 'active', and I can switch which one of those two is selected, but I can't see the mods anywhere to add them, and I can't figure out where on the screen they would be.
How do I modify my guns?