Steam Valve Gear Question

 When I brought the loco in to a friend, he noticed that the rods were not exactly opposite each other . They are at the present only 1/4 circle from each other.

They had better be, otherwise the real steam locomotive would not move. Remember that there is a "power stroke" every 90 degrees of driver rotation (referred to as quartering).

 In other words, the fireman's side is at 6 o'clock, while the engineer's side is at 9 o'clock.  First, is this right

Yes, very definitely.

(which I don't think it is), and second, how do I correct this misalignment if it is wrong?

Please don't try, otherwise you will break something.

At each end of a piston stroke, drivers and rods are on "dead center." The main rod is pushing or pulling across (or through) each driving wheel axle. Stationary steam engines have huge flywheels for momentum to move past "dead center." Steam locomotive drivers also serve that function. In theory, placing pistons and rods exactly opposite each other [12 o'clock / 6 o'clock] provides better balance. But in practice, if a locomotive stalls or stops on "dead center," it can't move without a nudge.

Not exactly. If the locomotive will not move forward because it is stopped "on center", moving the reverse gear into reverse, the locomotive will then move. The "lap and lead" tends to overcome the "stopped on center" condition.

A train creates more drag and makes the situation worse. Imagine a locomotive stalling on a grade or on a curve or in a station on "dead center" and blocking a track in both directions.

"Quartering" eliminates that problem. When one set of drivers and rods is on "dead center" [3 o'clock / 9 o'clock]  the other set is at mid-stroke [12 o'clock / 6 o'clock] and applies power to keep going.

Drivers are pressed onto axles with tons of force to keep them "quartered." Now and then a driver on a model comes loose but, like the big ones, they fit tightly.