Basically, here is some example code:
private Persona PedPersona;
private DateTime PedOneBirthday;
private Ped PedOne;
PedOne = new Ped("MODEL", Coords, Heading);
PedOneBirthday = new DateTime(*year, month, day*);
PedPersona = new Persona(*enter details here, include the PedOneBirthday variable in the birthday part of the constructor*);
Functions.SetPersonaForPed(PedOne, PedPersona);
And voila, you can now set peds as wanted, whether they are agents or cops, you can set their name, gender, age, citation amount, stop amount, etc.