It is easy! We'll get you set up no problem. You won't have to change any settings on your Mac for this one.
The problem is in your router, and you can access that without being wired.
Open Safari, or your favorite web browser, and type in the address bar 192.168.1.1
This will pull up a login box. Your login name is admin, and the password is either admin or there isn't one. When the password is accepted you'll be logged into the Router Management page.
Click on the word wireless and you'll see your Wireless Network Name (linksys) you can pick whatever name you want. Save Settings at bottom.
The sub-section Wireless Security provides you a place to enable encryption, such as WEP, which when enabled will require a pass-key to be entered before joining the wireless network.
Under Administration you can change the password to access the Router Management page from admin to something more secure. Don't lose it. Save Settings.
There are many things you can do to make your wireless network more secure, such as disabling the SSID Broadcast under Wireless, MAC filtering, different kinds of encryption, etc.
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