I haven't played in ages and just bought the Dragonborn DLC. Where does the questline that leads me to the new island start?

I figured I would get approached by a courier at some point but I've done a dozen quests last night and entered several main towns and so far nada.

Thanks,

You'll be approached. Just.....give it time.

You should be confronted by two creepy fellows at some point of the MQ quest 'The Way of the Voice'. At least be recognized by the Greybeards.

Or, you could just head to Solstheim. Head to the docks in Windhelm.

Get the horn of Jurgen Windcaller to the Greybeards. That triggers the game to start the Dragonborn questline. You'll know exactly when it starts.

After you're first visit with the Greybeards you should be approached by two cultivists.