I'm a great believer in the KISS principle.
Configuration is simple if you start from a factory default condition. Then connect the Airport to AC power and finally to the Internet modem (or modem/router). Open Airport Utility on your Mac or other computer and accept all of the recommendations. After confirming that it works, insert your desired administrative and WiFi passwords.
Do not expect the Airport to respond instantly to the configuration commands. BE PATIENT!
i have an airport express version 6.3 which i can not configure with my airport utility software nor update.
Philly_Phan has good advice for you as far as keeping things simple, but if your current operating system on your Mac will not support the older Express model that you have.....as I suspect is the case here.....it is going to take more than simplicity to solve your issue.
You did not tell us what operating system you are running on your Mac, but a guess would be Mountain Lion. Can you confirm on that?
If you do not know what operating system you are using on your Mac, click the Apple icon at the upper left corner of the screen and then click on About This Mac. Post back with the OS X version number that you see there.