In order to be able to add a shared archived report as a dashpart, you need a shared archive report list that users can access. To achieve this, you need to create a user who does all report archiving. Share their report archive by adding that user (username) to the web.config file. After the report archive has been shared, you can add a shared report archive dashpart using the Dashpart Configuration dialog box.
To setup a user to share their report archive list:
Stop the Web Services (IIS).
On the web server, open the web.config file.
Set the SharedReportArchive to the user who wants to share their report archive.
For example, if you enter <add key="SharedReportArchive" value="SYSADMIN" />, when you access the Shared Reports Archive drop-down list on the Dashboard Configuration dialog box, you should be able to see the SYSADMIN's report archives as well as your own report archives in the list.
Save the web.config file.
Restart Web Services (IIS).
Allow other users access to the report
Add a report archive dashpart to your dashboard
Add a report archive to the Navigation menu
Schedule the Delivery of a Report