word salad

I am having an issue with my gear. I have a behringer U-Phoria UMC404HD. This device has 4 inputs and I can only get Wavepad to recognize 2 of them. In mono it only recognizes channel 1 and in Stereo it recognizes channels 1 and 2 but not 3 and 4. How do I set up Wavepad to accept more than 2 channels at a time? I am thinking about purchasing the product but I won't if it cannot accept more than two channels at a time.