I download Dragonborn today and went to Windhelm. I talked to Gjalund Salt-Sage at the Windhelm docks for passage to Solstheim.

I arrived at Raven Rock and started doing some quests. I have just moved into Severin Manor and I want to start doing the Main Quest.

According to UESPWiki:

"Alternatively, you may take the Northern Maiden to Solstheim without yet being attacked, in which case you will have to pay Salt-Sage 250 gold for transport; you will later be attacked by cultists on the island and can find the note on one of their bodies there. If you choose this route, the quest will not be named in your journal, and you may miss out on certain dialogue options with various NPCs in Solstheim"

How do I get these "cultists" to attack me so I can start the Main Quest?

And what dialogue options have I missed out on?

Thanks