Thank you everyone. I used the guide though and found most of it out from there and from experimenting. I do have a question or two about triggers though.

Trigger trigger_t_lucretius_carus
WhenToTest CharacterTurnEnd
Condition EndedInSettlement
and RemainingMPPercentage = 100
and SettlementBuildingExists >= scriptorium
and IsGeneral
and I_TurnNumber >= 382
and I_TurnNumber <= 430

AcquireAncillary t_lucretius_carus chance 80

What does all of this mean? Thanks in advance. Oh, and is the chance out of 100, 100 being a sure chance and 0 being no chance? I really need to figure out how to use triggers right, or there's not much point of making the traits and retinue in the first place!