To add a comment to a cell, right-click on a cell and select Edit Comments. Then type in a comment and hit [Enter]. Comments are indicated by a small red triangle in the top-right corner of a cell. To view a comment, hover the mouse pointer over this small red triangle, and a small text box should appear with the comment. Right-click on a cell with a comment, and click on Edit Comments to change the comment for that cell. Right-click on the cell and click on "Clear Comments" to delete a comment.