Sorry, but your post is not clear. The topic of this thread is how to extend an AirPort Express or AirPort Extreme with a Cisco router.
This would mean that the main router was an AirPort device and the Cisco would be extending the existing network provided by the AirPort.
Is that really what you want to do?
If not, then it sounds like your Cisco ISP provided wireless router is your "main" router and you will be using the Time Capsule to extend the network.
Please start another post to tell us exactly.......
What device will be the main router providing your Internet connection and wireless network
What device will extend the network
What operating system that you have on your Mac or PC