Its explained a bit in the manual thats provided in the discussion sticky post, which culture are you ?

bretonnia and i found the manual that explains smthn

Fighting against "'evil" parties will give you chivalry, not taking prisoners will increase the gained chivalry, depending on career there's certain perks to give you some passive amount, having the pray buff active also gives you daily chivalry.

Having too many high tier cav troops that require chivalry upkeep can become too much, gotta balance it