How do you get new abilities in killzone 2

You go up in rank by getting points in Warzone. The higher your rank, the more abilites you are able to use. In order to get secondary abilities with your primary abilities you need to do specific tasks to get certain ribbons. For example, if you are a medic, you must first revive 5 people a match for 8 different matches in order to unlock the health pack ability. This is true for each of the classes except for the regular soldier you start out with.