To write simply, choose words of Anglo-Saxon origin over words with Latin or Greek roots. Anglo-Saxon words are usually shorter, and they tend to be specific and body-centered, where Latin and Greek words, as we use them, tend to be abstract and mind-centered.
As a writer, this helps you achieve two things. First, your prose will be easier to read because the words are shorter and more widely used. Second, the specific, body-related words reach your reader’s emotions more directly. It’s like a form of Deep POV based on word usage itself.
There are more Latin and Greek words in our language than Anglo-Saxon words, so again, you might have to look harder for a simple word than a long one.