Yes. You can alter your unconscious mind. Conscious thought and stimuli flows into the unconscious. Even though it isn't under direct control, gaining awareness of what the unconscious contains and altering consciousness thought through mindfulness and awareness techniques brings it to alignment with your conscious will. Gaining awareness of your complexes, resolving traumas and gaining awareness of your true self is the only way a completely free will exists. Some of the methods available are also dream analysis and meditation. Also choices that one makes in the media that they consume is a key factor. Closely monitoring thoughts that occur spontaneously during a quiet moment of attempting a clear mind reveals unconscious contents. Closely monitoring physiological responses and not acting on them reveals unconscious thought because physiological responses are originated in the unconscious mind and pushed through.

Reading recommendation: Strangers to ourselves by Timothy D. Wilson. Aware by Daniel Siegel. The Undiscovered Self by C G Jung.