It sounds like you're using the onboard audio of a computer, and that you've got the recording source in Windows set to "wave out" or "what you hear" or "stereo out" or the like. The immediate fix might be to go into the Windows audio settings and change the recording source to just the input. The more long term solution is to use a proper audio interface. If you are using an interface, you might be using it with the Windows drivers rather than the better ASIO driver that comes with most of that kind of hardware.
Omni a scale of complexity, it's certainly not the hardest - but with all of them, the learning curve is steep. Your problem will just be getting to grips with routing. You have routing within the DAW and you have routing in the interface, and getting them all sorted out takes time and effort - and some understanding of how it works, and for that - it's experimentation. Youtube videos don't help because everyone has different systems and different setups. Sorry that's not too helpful, but it's vital YOU work out how a signal applied to channel 1 of the interface gets to the channel you want to record it on, and then from there to the output channel, and output socket. In the DAWs, they all do it differently. I can't help you on Sonar, but others will be along who can.