I'm a little confused by your question. If you've already secured your router, you don't need to secure your Xbox. You need to connect it to your router via wireless if you don't want any cables. When you connect to your router, you enter the same key
on the 360 that you made for the router security.
I would advise not to use a WEP key though, it's an older obselete way of securing a wireless network.
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