The default password of the Airport Base Station would be "public.", but when joining the "Apple Network xxxxxx", I need a password of 8 characters?
What am I missing?
The password for the AirPort Base Station is for gaining access to the router for making changes to its configuration.
The password for the wireless network is for connecting to the network and the Internet from various client devices.
If you haven't entered a network security code for the network in the AirPort Express, then the network password would be blank until you enter one by accessing the AirPort Base Station using AirPort Utility and entering the Base Station password (public).