There's a new singleplayer expansion for Mass Effect 3 called Leviathan out today, but it's not readily apparent how to start it. Here's a tip: after you buy it and download it, check your in-game message terminal. You're looking for the message in the screenshot above.
This may seem obvious, but let's just say that some people wasted a lot of time searching their galaxy map for a new quest marker and went to the Citadel to fruitlessly scan their map for a new person to talk to. Wrong! We've got to check our e-mails.
That the beginning of this Mass Effect DLC is confusing is understandable. BioWare, clearly sick of people complaining about Mass Effect 3 endings, wanted to give people a Mass Effect beginning to grump about. Clearly. That has to be the case.
Anyway, this is how you start it. Thank you to Eurogamer's Tom Phillips for the tip.