I'm assuming that you picked some of this up from the YFM1 Wikipedia entry, herewith:
"The crew of five included the pilot and gunners; a copilot/navigator who doubled as a fire-control officer, using a Sperry Instruments "Thermionic" fire control system (originally developed for anti-aircraft cannon) combined with a gyro-stabilised and an optical sight to aim the weapons;[2] and a radio operator/gunner armed with a pair of machine guns stationed at mid-fuselage waist blisters for defense against attack from the rear".
As with other Sperry gyroscopic gunsights, the gyro likely stabilized an illuminated reticle projected on an angled glass lens in the aimer's line of sight to the target. I doubt that more than one person was required to operate it.
I checked my original YFM1-A Flight Handbook dated Dec 1940, and the only references to the guns are on this page. It make a brief remark regarding the location of the fire control 'box' in paragraph J, below, and that it seems only to have controlled the forward-facing cannons. Note that a primary function of the gunners (one seated on each wing in front of each rear-facing engine) was to load the cannons. As an interceptor with forward-firing cannons of limited traverse, it seems odd not to simply give full control to the fuselage-seated gun director.