One example of propaganda is "Beasts of England," the revolutionary song that Old Major teaches the animals in the first chapter. With lines like the following, it is propaganda for an animal revolution:
Soon or late the day is coming/Tyrant man will be o'erthrown/And the fruitful fields of England/Shall be trod by beasts alone.
Another example of propaganda is the set of rules known as the "Seven Commandments." These statements, which were distilled down by Snowball to a propagandistic slogan "Four legs good, two legs bad," were to be the guiding principles of Animal Farm, but the pigs changed them throughout the book as they became more and more corrupt.
Finally, Squealer's speeches in support of Napoleon are wonderful examples of propaganda. Squealer is so skilled that he is able to convince the animals the events they actually witnessed, like Snowball's heroism at the Battle of the Cowshed, did not occur.