What changes did Napoleon make first?
Other changes that may be more closely associated with Napoleon include assigning the windfall apples and milk to be fed to the pigs instead of the other animals. Squealer argues for Napoleon, as he typically does, that the pigs need this food to help them think and lead well.
Additionally, he begins teaching the new puppies to read; however, we learn he is really teaching them to be his personal security and he later uses them to exile Snowball. Shortly after, he no longer allows the animals to provide input into the farm’s operations and ends all public meetings. Instead, all decisions are made in private by the pigs.
If you are talking about literally the first change he makes -- the ones in Chapter 2, then his major changes are to destroy the symbols of human oppression and to put up the new 7 commandments that will summarize Animalism.
The first thing Napoleon does is to have all the stuff like the whips and chains and even the ribbons for the horses's manes destroyed. These were the symbols of how the people dominated the animals. He also has the farm house closed up.
Then he has the commandments painted up on the wall to show what the rules of the new society will be.