to look up the words in a thesaurus to see synonyms with different connotations. Additionally, I can read the words in different contexts to see how they are used and pick up on subtle differences in meaning. I can also consult with a teacher, tutor, or language expert for guidance on the nuances between the words in question.

make it sound like HUMAN and a 5th grader

To make your writing sound better, you can check a book that has words that mean the same thing. You can also read how other people use those words in sentences to understand how they are different. If you're not sure, you can ask a teacher or someone who knows a lot about language to help explain it to you.