Like a Blueberry Muffin

To be able to write, to only just write, all you need to know are the words. To teach or to talk about those words you need to know more than that. but to just write, the words are all you need.

It's like baking. To bake you don't need to know that flour is called flour, sugar is called sugar, that blueberries are blue berries, or butter is butter. To talk about baking, or to inform someone how, you need to know what the ingredients are called. But to simply bake all you need know is precisely what those ingredients are. Then you will know how much of each to use, how to combine them together and when to make that blueberry muffin.

To write and nothing else, just know your words and how and when they should be combined to impart what it is you mean say.