Are you sure this is BES 4.0? Check Help>About again and make sure that you have opened the BlackBerry Manager and not the Handheld Configuration Utility.
If this is BES 4.0, then my previous instructions are correct. If it is BES 4.1, then use these instructions:
1. Open the BlackBerry Manager
2. Click on BlackBerry Domain
3. In the Tasks area, click License Management under the Account heading
Those are from this RIM KB: BlackBerry Search Results
So, if these are wrong you are looking at the wrong Manager or it's screwed up.