There are 2 places that you may add Case Managers within a Client Profile (see Finding a Client Profile). The first is in the Client Details section then selecting the Edit Settings tab.

You will find the Case Manager field near the bottom of the page.

The other is when adding or editing a package schedule in the Client Profile. Open the profile as above and choose the Package Schedule tab.

When selecting either Add Package Schedule or selecting the link to an already added package you will open the package and see a required field to add the Case Manager.