Frankly, I am uneasy about some of the things that you are relaying here.
I have no idea why Apple would have advised you to "create a new network" since you would not do this unless the AirPort Extreme were to be permanently connected to the Time Capsule using an Ethernet cable connection....and you indicate that you want the AirPort Extreme to connect using wireless.
If you want to try to setup the AirPort Extreme again to connect using wireless, here is what I would suggest.
Temporarily power off the AirPort Express devices to prevent conflicts during the setup
Make sure that the Time Capsule is not backing up at the moment, and then power it off, wait 15-20 seconds and power it back up
Remove any Ethernet cables that might still be connected to the AirPort Extreme, and then locate the AirPort Extreme in the same room or close proximity to the Time Capsule for the setup
Power up the AirPort Extreme for a few minutes
Hold in the reset button on the back of the AirPort Extreme for 8-10 seconds and release, then allow a full minute for the Extreme to restart to a slow, blinking amber light
On the iPad home screen, tap Settings
Tap WiFi
Look for a listing of Setup A New AirPort Base Station
Just below that, tap on AirPort Extreme
The utility will open up and take a minute to analyze the network, then suggest that the AirPort Extreme will be configured to extend the Time Capsule network
Enter a name that you want to call the AirPort Extreme, then tap Next
The utility will setup everything for you. When you see the message of Setup Complete, click Done
Move the AirPort Extreme to the desired location and power it back up, then power up the AirPort Express devices