How do I enable Model Item Security in Reporting Services 2005?

Question

For the life of me I cannot figure out how to enable model item security on my models in RS2005. Pages such as:

http://msdn.microsoft.com/en-us/library/ms365305%28SQL.90%29.aspx

Imply that I need to connect using Management Studio...

However, when I connect with Management Studio the only things I get to manage are:

• Jobs
• Security (Just contains the standard roles for the reporting server)
• Shared Schedules

No mention of models or model security anywhere...

Any ideas?