Joining the knights is a quest you get in New Bartuio.
What to doEdit
You go to the knight captian and ask to join.He will ask you to eliminate a Dragon of Hallow which is in the Fort Hallow.You go there and find no dragon.Reilizing you where ment to die you head back to confront the knights.
Upon Confronting the leader,he reveals that new members had to be more than just a simple Dragon Slayer or petty Adventurer.You can ask him to join again,but he still says to do something important,you can however,join the knights properly by finding Captain's Note,revealing he is taking large shares of all Count Bartuio's royal earnings.
The Player can show the Count this evidence,the Player is then awarded the immediate title of Head Bartuio Knight.They are also allowed to execute the previous captain in anyway they choose.If they player makes him fall down the stairs they can earn 500 gold.Easy Money!
If you have been to Hallow you can skip it saying there are no dragons there.