This really is the wrong place for such a basic question!

None of the airlines you are travelling with are oneworld airlines, so your status means absolutely nothing. You will not be able to use any oneworld lounges while travelling with Icelandair, United, or Virgin.

You will have to ask each airline (or better: check on their website) to see what lounges they use in whatever airports you will be departing from with each individual airline.

You will not have lounge access on any flights in Economy class - lounge access is granted only in advance of those flights for which you are travelling in business class. Ask at check-in. You really don't need to know anything about the lounge until you get there.