In the shooting phase, a player may freely pivot a war machine to face any direction he likes before shooting. Apart from this, a war machine may not be fired in a turn when the machine itself, or even just its crew, have moved.
Normally, the controlling player must be able to draw a line of sight to the target from the machine itself.
Each type of war machine is fired differently, as described in its own set of rules. For now it is enough to know that some war machines are fired like normal missile weapons and so make use of the crew's Ballistic Skill, but other machines require you to guess the distance between the machine and its target and make use of the artillery dice and the scatter dice. The scatter dice is the dice marked with arrows on four sides and the HIT symbol on two sides. The artillery dice is marked 2, 4, 6, 8, 10 and MISFIRE.
Remember to always start the shooting phase by guessing the range for all war machines that require you to do so.