The PEE technique is a method for constructing arguments in paragraphs that revolves around three steps: Point, Example, and Explanation. It is a good way to articulate your thoughts in a clear and concise way.
The first step for this assignment would be to make a point. This is very akin to a thesis statement. For this question in particular, one example could be as follows:
The Pigs betray Old Major's vision of a social utopia by slowly undermining equal distribution of labor, rewriting the core tenants of Animalism, and exploiting other animals for their own gain.
The next step would be to show evidence for your case. Animal Farm is full of evidence to suggest that this is the case, with some of the most profound scenes featuring Napoleon being deaf to the plight of the animals, betraying their trust, and changing the very nature of the society that they strove for through his mouthpiece, Squealer. One of the most telling moments is when he is making deals with the humans, completely indistinguishable from them at this point.
The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.
Finally, your job is to create an explanation for this point. This is where you will insert your own ideas about how the evidence backs up the point. It is clear by the end of the book that the pigs have betrayed old major's cause because of how they have become indistinguishable from the humans that they sought to overthrow. The pigs have so completely perverted Old Major's dreams into gain for themselves that the creatures, and the readers are left to wonder if the old pig himself might have been equally corrupted by power if he had been given the opportunity.
This is just one example of an approach you could take for a PEE assignment of this type.