Most of that is random errata. Very simply, you give orders to Velmu, who works them out simultaneously. All orders are either move or support orders. A move is either that, or an attack, depending on what is in the territory you are moving to. To attack an army, you need two in the area, one of which supports the other.
A sample order:
Fleet Edinburgh -> York.
Fleet London supports Edinburgh -> York
I have now ordered my fleet in Edinburgh to move to York, with the support of my fleet in London. The support order means that if an enemy unit was in York, it would have to retreat, unless it, too, had support. Now, if there was no enemy in York, that support order would be meaningless, since you don't need support to move into an empty territory.
That's the very basic gist of the entire game.