Once per turn, the Steam Tank can fire its hull-mounted weapon against targets in its 45° frontal arc (see diagram 1). This costs 2 SP and can be done even if the Tank has moved, as long as there are enough SP left.
Once per turn, the Steam Tank can also fire its turret-mounted weapon against targets all around. This costs 1 SP and can be done even if the Tank has moved, as long as there is 1 SP left.
Rotate the turret so that its gun is pointing towards the intended target. This is important if you are firing a gun that makes use of the Flame template, because it will determine the point where the template is positioned. If the turret is glued in place, just measure the distance of the barrel away from the turret in the intended direction and place the template there (basically, imagine that the turret has turned towards the target). The Steam Tank can fire both guns in the same turn, as long as there are enough SP left.
The Steam Tank can fire its hull- mounted gun and turret gun even when engaged in close combat. It can even fire them against the units engaged in combat with the Tank, provided that there are no chances of hitting friendly models, or enemy models that are in base contact with friendly models other than the Tank.
Remember that the Tank is a large target, so it can see over enemy troops and target enemies far away even when it is engaged in close combat.
If the Steam Tank is not engaged in close combat, the Tank commander can pop up from his hatch and fire his repeater pistol at the enemy (he has a 360° arc of sight and can see over intervening troops). When the Tank is in close combat the commander will not risk coming out and therefore cannot shoot, but he is allowed to stand & shoot with his pistol when charged. This is the only kind of charge reaction allowed to the Steam Tank other than holding its ground.