The new dashboard allows you to publish custom reports to it and to edit the reports that have already been published.
As long as you have access to the report you will see this edit button above each report in the dashboard. Select this button to be taken to the view tab of the report builder tool.
From here you can select the Edit button to change the report itself, or the Publishing button to change the publishing settings.
For more information about editing a custom report see: Custom Reporting
You will then see this page. Make sure to select View Published Tables and Charts and then find the table or chart you want to edit and select the Edit button under the actions column.
This will take you to the same page that you would see if you were publishing the chart for the first time.