To logout from the SIRI portal, in the Dashboard page, click on the  icon located at the top right side of the page.

Then a menu will appear. Click on the 'Log out' menu to log out from SIRI portal.

If you want to stay sign out of the SIRI portal, click on the 'Yes, Sign me out' button. Otherwise, click on the 'No, Stay Signed In' button to remain signed in to the SIRI portal.