The player may also compete for the title of King of Pendor, but if he does so, he will have to beat all 5 kingdoms, instead of 4 with the help of the one he joined. Upon capturing your first fief as a freelancer, you will take it for yourself, starting your own kingdom.
Talk to your minister (you should try to assign this role to your wife (if any), else a companion) for the first time so that he welcomes you and asks which culture will the kingdom be based on. The player will be able to choose between the 5 existing kingdoms' cultures, or the Pendor culture. After this, he will ask you to select a crowned helmet of the 11 possible ones (the 5 of the other monarchs, the 5 from the claimants, or the helmet of Pendor. Here are their names and models:
Note: you will always get 2 Royal Crowns (one is meant for your spouse) + the helm you decide. All helms have the same stats (60 head armor, 6 body armor) except for the Royal Crown (24 head armor)
Your next step is to hire a Mercenary Company to support you in defending your new kingdom, mainly against the kingdom you took it from, as they will attempt to reconquer it. You should make some companions into lords of the villages attached to your walled fief (castle/city) so that they can start gathering an army as soon as possible. Make sure to appoint companions that are nobles with either good natured or upstanding personalities (in particular Sir Roland); this will make it immensely easier on yourself. Telling your steward to start training troops to raise a garrison will be helpful in restocking your army and defending against the initial siege. Do not travel too far from your holding as that may lure enemy lords to attack prematurely.
After successfully defending against the initial siege, you will now be able to counter-attack and absorb the now weakened kingdom. How you handle the rest of the game is up to you!
This video provides a guide that gives you steps to a successful playthrough all the way from character creation to managing your kingdom and finally conquering the world: