How do you pillage in ikariam?

How do you pillage in ikariam?
Build units at the barracks, and build a port, then select someone from the island view and click pillage, you may need to blockade them first, build a shipyard to do that.Build units at the barracks, and build a port, then select someone from the island view and click pillage, you may need to blockade them first, build a shipyard to do that.