Your account must first be setup with a Quarantine for this to work.
1) Create a new folder in Outlook.
2) Call the folder "Spam" or "MessageLabs-Spam," ( or whatever you chose to name it ) and when prompted add an Outlook shortcut to the shortcut list. The shortcut will be placed on "My Shortcuts" but can be moved to the other Shortcut lists as necessary.
3) Right click the "Spam" folder, select "Properties".
4) Select the "Home Page" tab in the Properties window.
5) In the address window type the following URL and select the checkbox labeled "Show home page by default for this folder":
https://us.quarantine.symantec.com/enter your email address here/
6) Click "Apply" and "OK".
7) Click on the Spam folder, login to your Message Center and if desired, select "Remember my Address and Password"
8) Close Outlook
[ The next time Outlook is opened and the Spam folder is selected, the Message Center should appear within Outlook.]