To delete a graph or to remove a few charts from a dashboard: Click ‘Edit’. Scroll to the relevant graph. Click the small red bin (or trash can) in the upper left corner of the graph.
Remember to ‘Save changes’.
To delete an entire dashboard or graph set: Select the dashboard you wish to delete, then click the three dots at the top right of the page. Select ‘Delete’.See here for an overview on editing dashboards and here for more specifics on moving and deleting graphs.
WARNING: THIS WILL REMOVE THE DASHBOARD FOR ALL USERS.