We assume that the Expresses are also connected using a wired connection.
You cannot "extend" with a wired connection since the "extend a wireless network" setting will only work with a wireless connection between the Time Capsule and other AirPorts.
Configure the AirPort Expresses to "create a wireless network" that uses the exact same wireless network name, same wireless security and same password as the Time Capsule network, and you will have a "roaming" network, which is far superior to an "extended" network in terms of speed and reliability.
If you are thinking of trying to extend the Arris WiFi network using a wireless connection with the Expresses, this is not possible, since Apple's "extend a wireless network" setting will only work with other Apple routers.