You cannot resize the overseer interface windows on a laptop. Looks to be the same sort of interface fail we got with monster missions.
On my laptop, I can resize the window, but I can't make the window tall enough to be able to assign agents. That was in windowed mode. I had to go to full screen mode and increase the display resolution to max. For me that was something around 1300 x 800. At that point I could just barely get to the button to assign an agent to a slot.