Make sure you have your new Username and password handy - to check these details, contact the My Telecom helpdesk.
Follow the supplied product documentation to setup your AirPort express to suit your local requirements. As a final step, configure the AirPort to use PPPoE login to MyTelecom, a screenshot of the required configuration is provided below.
If you are having difficulty setting up PPPoE on your Broadband router, you can ask MyTelecom to check your username and password. We can also check login records for your username to see if there are any connections trying to go through.
Unfortunately, MyTelecom's technical support team does not maintain a working knowledge of Apple's networking products. If the login details appear to be ok, and the problem seems to be related to the Airport setup, please contact the manufacturer for further support.
If you have good reason to believe the Airport is okay, try to prove the connection does not work either with a normal pppoe connection (e.g. straight to a computer). MyTelecom's final support obligation in these cases is to send a technician with a test laptop to confirm the connection itself is okay.