When you're in one of your documents, use the cursor to highlight a word. Then, click the light bulb icon on the farthest left side of the menu bar. Now, you'll be able to look up synonyms, antonyms, definitions, and examples of the word you've highlighted. If you'd like to replace the word you've highlighted with one of the synonyms, simply click on the synonym. If you change your mind and want to go back to the original word, click Control and Z twice.