If you want to keep your dashboard list from becoming too cluttered, you can delete a dashboard if it is no longer required. This can be accomplished in one of two ways:
Dashboard Options menu - this method requires you to own the dashboard or have Edit permissions.
Click Account Settings > Dashboards.
In the list of dashboards, click the dashboard you want to delete.
Click Delete Dashboard.
Click the Dashboard Options menu at the top of the screen.
In the dropdown, click Delete.
When prompted to confirm, click Delete.