Scatter
When a rule calls for something (a template, a counter, even a unit) to be placed and then scattered: place it as instructed, then roll the scatter die for direction and whatever other dice the rule calls for to determine distance. Roll as close to the scattering object as practical, to minimise drift. War machines typically use the artillery die for scatter distance.
A Hit! result means the object doesn't move at all -- resolve the rule from where it already is. An arrow result moves it that many inches in the direction shown, ignoring anything in the way unless the rule says otherwise. Once it's landed in its final position, resolve the rest of the rule.
Choosing a Random Direction
Some rules just need a random direction rather than a full scatter. Roll the scatter die and use whichever way the arrow points -- if a Hit! comes up instead, use the small arrow shown on the Hit! symbol itself.