In documentation says:

http://octobercms.com/docs/backend/widgets#report-widget-registration

The label element defines the widget name for the Add Widget popup window. The context element defines the context where the widget could be used. October's report widget system allows to host the report container on any page, and the container context name is unique. The widget container on the Dashboard page uses the dashboard context.

and how to place on any page of my plugin? thank you