On apps or reader view, click on the edit icon of the tab you want to share. If necessary, uncheck the "Library tab" option and then click on the share button.
The Share panel will appear with the web services configured for your account. To share the tab by email, click "By email" and a form will appear to fill out.
Your recipient will receive a link to a pre-configured tab based on your selection of sources (feeds, tracked topics, analytics and custom apps are currently supported). Note that analytics can only be shared between copies of the same Premium Dashboard. Sharing between separate Premium Dashboards is only available on Netvibes For Enterprise with the Hierarchical Dashboards feature.