What part of a plane adjusts the curvature of the wings in order to create lift?

That would be the flaps. There are flaps on the trailing edge of a wing on most aircraft and there can also be leading edge flaps as well, often seen on the big airliners. These flaps will be lowered and will effectively increase the curvature of the wing, allowing it fly at higher angles of attack for greater lift. It also produces greater drag, useful for dropping altitude without speeding up and flying slow on approach to landing.