Where was Eve before she was brought on the scene in Genesis 2?
Before Eve was brought on the scene in Genesis 2, she was still in Adam. She was not yet a separate individual; she existed within the first man, part of him, prior to being formed and presented to him. She was not yet on the scene.
Les explains that in Genesis 2, before the Fall, Eve isn't even on the scene—just Adam. Eve is still in Adam. This means she was not yet a separate person but was contained within Adam prior to being brought on the scene. This illustration is part of a larger discussion in Ephesians 1 about the church as the complement of Christ, but the immediate point is Eve's prior existence in Adam.