I don't remember it popping up automatically.
Once I got to lvl 20 a lady in the main militia house in fp finally responded to me and then started off the quest to become sk. Reason I remember it is because 20 is when you can buy our steed for 14s too.
Before lvl 20 the lady in militia house doesn't respond. Pretty sure it's North freeport, whatever militia house. Upstairs one flight on 2nd floor.