You will not be able to add widgets to the curated reports by default. 

In order to modify them, you will have to Clone the Report. 

  • Go to a Curated Report.
  • Click on the three dots next to the name of the report.
  • Select Clone Report and modify the name of the report to your preference.
  • Click Copy.

Now, you can click Add widgets and Drag and Drop a chart to start building the widget.