To enable authentication for a codebase server, go to the Application Assembler's Codebase Locator Definition window. In the Authentication Information group box, fill in the End-User Description field. Then, check the Prompt for ID/Password (Unless Cached) box, and finally, if the codebase server is an AppServer, check the Prompt for AppServerID/Password/Info String (Unless Cached) box:

Enabling this option displays the following authentication prompt to the end user: