making butter at home is a very simple process - there are many many ways to do it.
I use a stand mixer with a whisk and heavy cream from the supermarket.
put the cream in a bowl, whip slowly at first until it froths, then increase speed until you get butter.
you will see the cream go to whip cream, then over beaten, then grainy, then lumpy and now you have to be careful because as the butter 'falls out' of the cream you're left with the watery whey aka (real) buttermilk and if you don't slow the mixer down it spatters all over.
there a zillions of videos etc.