Napoleon takes the young from their parents and educates them himself, pigs in particular. He took the nine puppies first and trained them to be loyal to him and ferocious beasts that would do his bidding, then he began to impregnate the sows of the farm and take them at birth to teach them the principles on which he desired Animal Farm to live by. He taught the young piglets that they were better than other animals on the farm. He taught them that other animals should move out of their path if they were on it. He taught them to read and write and communicate so that the pigs would always be leaders on the farm and no other animals could rise above them. He kept the adults ignorant because they weren't fully literate, he only taught them small things, but nothing to empower themselves. He appealed to their short memories. He didn't educate them or allow them time to become educated because they were either working or sleeping, they had no time for education because it was their duty to work and the pigs' duty to learn and to lead.
In order for Napoleon to indoctrinate the young, he takes them away from their mothers when they are born. In doing this, he can teach them to follow his commands. Since they learn Napoleon's ways from a young age, they will know no other way to live; as a result, they will forever be sacred and committed followers of Napoleon and his government.
Napoleon Kept the adults ignorant by not educating them. Since the other animals could not read they did not know when Napoleon was changing the laws (laws that were only favoring Napoleon and his "men"). Napoleon also convinced the animals, from early on, that he was there to protect them from any evil and that he would never let them be treated poorly again. The animals, not knowing any better, became blind followers of this. When things did go wrong, they always reverted back to the belief that Napoleon was good. He also trained Squealer to go around and convince the animals of this if any animal questioned anything that happened.
Napoleon had absolute power. The animals he ruled over were uneducated, and because of this, they did not know that they were being "had". He kept them blind to what was going on. He also exhausted them by making them work long hours on little food. This made the animals too weak to think reasonably or argue against what was happening.