Hi everyone im NLjeroenNL and i just bought Dragonborn and i wonder how i trigger it is it the same as dawnguard (a specific level) or a quest line please tell me what to do to trigger it like quests completed/level/skill etc.?

If you wish to trigger the dlc's main questline you need to have atleast activated the quest "the horn of jurgen windcaller" (Part of the normal main questline). Afterwards you will be randomly attacked by cultists in one of the cities and they will carry a note.