You need to be in view mode in order to add comments and attachments.
Select Comments and Attachments from the report toolbox list in the upper right corner to open Attachments panel.
Attachments dialog allows you to add:
Hover over desired table cell and select comment to attach comment to the data.
Red triangle marks cells with attached comments. Hover over the cell to see the bubble with the comment.
Hover and click on desired values in the chart. The value settings popup will be opened. Type comments and hit Add.
Comments will be recorded:
The Global comments feature needs to be enabled in the domain administration.
When the global comments are enabled, the comments are propagated to all the views based on the context (indicator and attribute) applied in the view. Global comments are propagated to tables, charts, and KPI labels.
When the global comments are enabled, the comments panel displays all the available comments from all the reports where the user has access.