If you receive notification of a class action lawsuit that applies to you, you must decide whether or not you want to participate in the suit. In most cases, you are not required to opt in. Rather, you will be notified of the class action lawsuit via mail or email, and you will automatically be part of the class. Except in rare cases, no further action is required on your end. If you choose to be part of a class action lawsuit, you will receive any awarded compensation, but you waive your right to file an individual suit against the defendant.
Alternately, you may choose to opt out of a class action suit. You will not receive compensation if the class wins in court. You will, however, be free to bring your own individual charge against the defendant. If you believe the injuries you sustained are significantly larger than those of the other members of the class, then you may benefit from opting out and individually pursuing damages.