When you enter the Record Control screen within WavePad, you will notice the Recording section on the right hand side of the window. Simply select the correct input device for your USB cable. Windows generally recognizes these as new devices and as such you will need to select it manually if you wish to use it. If you are going to be using this input device more often, you could go into your Windows sound and device settings and set this device to be the default input device, which is what WavePad generally uses for receiving audio.
