As this question is specifically on Kant and not the moral arguments in general, you could begin your answer by explaining his understanding of the categorical imperative. As this is a philosophy answer and not an ethics one, there is no need to compare it with the hypothetical: just focus on the parts of Kant’s argument that lead towards the postulation of God’s existence. So you will need to explain Kant’s belief in the rationality of morality and that, if a maxim is irrational, then it is immoral. This might lead you to the summum bonum and the fact that this belief itself is irrational given the state of the world, unless we are immortal and in the afterlife you postulate a God who brings about justice and happiness. Be clear that for Kant this is not a proof of God’s existence but rather something he postulates.
Here you may have to introduce some AO1 material to develop your answer, e.g. you could describe what Freud or other atheists believe about the source of moral awareness in order to critique the statement in the question. As you describe these views it is helpful to evaluate as you go along, so for example, it is better to say that ‘Freud is right or wrong when he says x or y because…’. The assessment of your answer will be based on your evaluation, not on your knowledge of Freud or others. Equally you could argue that, without a belief in some sort of divinity, there would be no morality.