Google Doc Help
Please choose the suggesting mode in the top right
You can then make editing changes to the text and it will automatically track your suggestions, which I can then accept or reject.
If you wish to comment, select the word or section you want to comment on, and then move your cursor to the right margin and a comment box will appear.
You can then “talk to me” by making a comment (rather than a change).
Don’t forget to click the “comment” button to save your comment.