Hello, my name is Rusty. I'm a sound engineer, I can help you. That board luckily has enough features to make this happen. The trick is to avoid a feedback loop, which is very tricky to do.
Connect your microphones, and other broadcast gear to channels 1-8. Connect the main outs to your computer's microphone input. Connect your speaker out on your computer to channels 9-10. Be sure the button near the 9-10 fader is set to MON, not st, so it will be pressed in.
Now you will be able to have a skype conversation. You won't use the USB configuration with this setup. Let me know if you have any trouble.