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To use your Time Capsule from your Mac, you must have Wi-Fi turned on or you have to connect your Mac to the Time Capsule with an Ethernet cable.
Also, the Time Capsule doesn't show up on iTunes. Instead, the Time Capsule show up on the Finder sidebar, under "Shared", to store things, and when you want to turn on Time Machine, because the main Time Capsule feature is that you can use it to back up your computer with Time Machine.
If you want to modify the Time Capsule settings or you have to set up the Time Capsule, open AirPort Utility and follow the steps