How does the occupation system work? When I click a planet and click occupy, the option for it in the fleet menu is greyed out. The only time I have ever seen it not greyed out is when targeting a debris field or a pirate. however according to the direction occupation takes 10% of a players resource production..... and there is a selection for "Occupy" when you click a planet along with attack espionage etc.
 
Do I need a certain type of troop to do it? I have not seen one with such a description.
 
Thanks.