i know how it all works haha just wont let me cos hes in a quest apprently. Got over 600hrs on the game, its use to do it just refuses too in my new campaign
if your clan is Tier 4 you click create kingdom at the top of the clan page. You also have to own a castle or city before you do this
when they finish the game as a singleplayer though they really should look into doin it. the game would be perfect if i could play the campaign with friends. either as a allied clan/ same clan or even a opposing kingdom.