The AirPort Express Base Station (AX) can store up to five different
configuration profiles. You will need to use the AirPort Utility, located in Applications/Utilities to create & save these profiles.
To create a new profile:
o Open AirPort Utility, select your AX from the list, and then, click "Manual Setup."
o From the AirPort Utility menu, select "Base Station," and then "Manage Profiles."
o Click "+" to create a new profile; give it a name, and then, click OK.
o Set options, such as network name, passwords, Internet connection method, etc.
o When done setting the options, click Update.
To switch profiles:
o Open the AirPort Utility, select your AX from the list, and then, click "Manual Setup."
o From the AirPort Utility menu, select "Base Station," and then "Manage Profiles."
o Click on the desired profile, and then, click OK to apply the new profile and restart the AX.
Just remember to switch to the desired configuration profile before removing power from the AX.