If you're to that point in the tutorial, there's not much left to do except use an assassin and take another castle. The assassin is dead simple to use, select him, right-click on a target, examine his chances of success, and go ahead with the mission or not. You already know everything else the tutorial has to offer and it doesn't impact the campaign game at all. Unless you're a completionist, I'd say exit the game and start up a real campaign.
As a bit of advice, if you're offered the option of ending a battle early in a siege, take it. Much less tedious, and the enemy garrison dies on the campaign map anyways as it has nowhere to run.
Bookmarks