Structural theory of the mind:. Teach the relative power and functions of the id, superego, and ego, and how pressure on the ego leads to defense mechanisms.Teach what is unconscious and what is not. Don't bother talking much about dreams or free association.
Psychosocial stages: Teach the stages of development, oral, anal, phallic, latency, genital, including the potential for psychopathology when things go wrong in the satisfaction of different stages. Don't bother going into detail about how the Oedipal drama leads to development of morality.
Determinism: Explain how Freud is a determinist and compare to a humanist such as Carl Rogers (link here) or an existentialist. (See my comparison to existentialist Nietzsche here.)
These concepts can be taught with one lesson. If sophomores understand the above, you have done well!
In order to help you along, here is a two-minute overview video explanation of much of the above. A fun skit is here.