All you need to do is inflict 750.000 Damage with ships of Tier 6 and higher and you get a port slot for free.
http://www.himmelsdorf.com/wp-content/uploads/2016/03/6ct9E7m.jpg
(source: himmelsdorf.de)
http://www.himmelsdorf.com/wp-content/uploads/2016/03/6ct9E7m.jpg
