You need to do nothing. Once a "lead" prosecutor for the shareholders has been established (with a lead plaintiff designated and qualified) the other firms may either drop their case, or join up with the lead firm.
Regardless, you don't need to do anything. The plaintiff attorney will research all the stocks purchased and sold during the class period, and that will turn up your name & mine, along with our addresses. They will notify us by mail, and usually you don't have to do anything to be part of the class action suit and settlement.
If you want to give up your rights, and not participate in the suit or the settlement, you can sign a waiver, send it in, and it won't change anything except the rest of us will get your share of the settlement.
Truth be known, the settlement will likely be small (if anything) after the attorneys fees, but depending on how many shares you owned, it can add up. It will all be a function of how much the settlement is, then subtract attorney fees, and divide the rest by the number of shares to determine the "per share" amount -- then multiply that by how many shares you have (the attorney will actually do this for you).
I'd give my share to the lawyers if they could have Duffield removed.