Apple's AirPort Time Capsule is a two-in-one device that provides high-speed wireless networking and up to three terabytes (TB) of back up storage. While it is designed to be the backbone of an all-Apple home network, it can handle both Apple and non-Apple wireless devices.
Plug the Time Capsule into a power outlet. You should see the small light on the front glow amber, then blue. When the light is blue, the Time Capsule is ready to be configured. (See References 1, page 12)
Plug the ethernet cable into the back of the Time Capsule. Plug the other end into the DSL or cable modem provided by your Internet Service Provider. This connects the Time Capsule directly to your Internet connection and allows the Time Capsule to share your Internet connection wirelessly with your devices.
Download and install the Apple AirPort Utility from the Mac App Store or from Apple's website at http://www.apple.com/airport-time-capsule/. The AirPort Utility will ask you questions about the type of network you want to set up or join, and will guide you through all of the setup and maintenance tasks you'll need to perform on your Time Capsule.
Open the AirPort Utility. It will begin scanning for available wireless networks. When it finishes scanning, you will see icons and descriptions of the wireless networking devices it has found. If you do not see your new Time Capsule, click the "Rescan" button.
Click the image of your new Time Capsule to begin configuring it. Follow the onscreen instructions to configure the Time Capsule on your existing network. When the Time Capsule is fully configured and connected to your existing wireless network, the light on the front of the unit will change to green.
Choose "Extend a wireless network" as your network mode. This will prevent the Time Capsule from attempting to set up a second wireless network, and can extend your wireless range, depending on the placement of your other wireless router.
The option to enable a guest network will allow visitors to connect to the Internet via your wireless network, while keeping your printer, file storage, and other devices off limits. Set up a password for your guest network that is different from the one you use to secure your main wireless network. (See References 2)