A novel as complex and multi-faceted as this one offers many different ways to apply Freudian psychoanalytical theory to the text (and many avenues for the application of other modes of critical theory).
To take a broad approach, we might begin by trying to situate the novel in terms of the Id, Ego and Superego and identify elements of the text that match this Freudian structure.
In doing this we might identify Moby Dick as a representative of the Id. Living underwater in a metaphorical subterranean state and a literally submerged one, Moby Dick may be seen to symbolize the blind and chaotic forces of the unconscious mind.
Captain Ahab, bent on establishing mastery over the chaotic world of the sea, may be taken to represent the Superego. While he is not "civilized" in all sense, Ahab is definitively associated with a will to control, a will to power, and a penchant for subduing any force that would contradict him.
“There was an infinity of firmest fortitude, a determinate, unsurrenderable wilfulness, in the fixed and fearless, forward dedication of that glance.”
The crew then would be the Ego, managing the conflict between the opposing Id and Superego. The crew is both self-representative and is symbolized (via synechdoche) by Ishmael, here the Ego par excellance, conscious and aware of a pull in sympathies going in both directions.
We might further consider the novel in terms of wish fulfillment (as Ahab is compensating, perhaps, for a childhood deficiency or trauma in his desire to either kill Moby Dick or sink the Pequod, or both).