Unbolt the lower control arms, put washers between the control arm and the body of the car. Tighten the bolts back down.
Its as simple as that. The more washers, the higher the positive camber you impact on the rear wheels. I dont know how long the rear bolts are, so im not sure how many washers you can safely put in before you are reaching the limit of the amount of threading that needs to be in the body.
