5) You should see 3 columns on the main menu. In the middle column somewhere is Wireless. Click that.
6) One of the options is Wireless LAN or Wireless, and another should be WPA/802.1x. I'd choose WPA/802.1x, since WEP (available under the Wireless menu) is not very secure.
7) on the WPA/802.1x menu, choose Authentication Required, then choose WPA-PSK as the method/encryption. My mind is a bit hazy on what options are available, but those 2 options and the Pre-Shared key box are the only 3 you need to be concerned about. Choose a password that's 8 characters or more (letters and/or numbers), write it down, then click Apply/Save.
8) At this point, you'll have to get your wireless computers to reconnect to your wireless network and type in the pre-shared key to connect.