Final answer:
You can customize a message by clicking the Edit button next to it, and you can add comments via the 'New Comment' feature after highlighting the part you want to comment on. Remember to save changes after editing.
Step-by-step explanation:
You can customize a message by clicking on the Edit button to the right of a message in the editing area. To modify the content, you may need to click the Edit page button in your user bar. Once clicked, a suggested structure for your content will appear, allowing you to add your new content. After making changes, ensure you hit Save to keep the updates. If you wish to add comments to specific parts of the text, first highlight the word, sentence, or phrase you want to comment on, and then click New Comment in the tools ribbon to create a comment box in the margin. Here you can type your comment. Remember, any edits made directly to your document may appear in red to signify added text, or red text with a strikethrough for deleted text, ensuring changes are easy to identify.