You always have the one "Ask the Audience" lifeline in round 2 which is good for 1 correct answer.
What happens is, you get a question you can't answer so you click on the lifeline and the game stops. In a few seconds, a window opens and a list of friends will come up and you can pick who you want to send the question to. I don't think it matters what you do here. For a long time, I was just closing the window without clicking anybody. Then I realized I should probably be clicking somebody. Maybe you can click a whole bunch of people - I don't know.
It doesn't matter if they are online. They will deal with the question later and I guess if they answer correctly, you get some lifetime points or something.
Then another window opens up. I think it is trying to get you to spam your friends but I don't know - I just shut it down.
But the point is, after you click Resume Game, you get credit for a correct answer and move to the next question.
I'm sure I read that you can't use that lifeline for the million dollar question so if you do get the first 2 questions right, you should always use that lifeline on your 3rd question. No reason not to.