Seats in the centerline mounted (one for loader, one for launcher operator). The loader's seat (rear) can be turned 360°.
Right side missile loading system extended in loading position, left side folded back against side wall to increase available space for occupants. Each of those loading arms mounts a pair of missiles on top and another on the bottom, with the loader able to just flip it over to load the other side.
View from the loader's seat, with right-side missile loading arm in the folded-back position and missiles mounted. The cans that you see on the wall in the crawlspace towards the front are ammo cans for the machine gun on the commander's hatch. 3,500 rounds.
P.S. Note industrial-design joystick for the launcher operator to remotely move the launcher.
For demonstration - missiles on left side mounted, loading arm in loading position, hatch to launch recess opened for insertion (launcher is in the up position though), right side loading arm folded back, loader's seat turned 180° to the back, wooden slats on floor to prevent sliding:
People for scale; in my opinion - from experience in similar other vehicles - the VAB has a relatively high interior: