Hi. It looks like that amp has pre-amp outputs. Is that correct? If so, then you have at least two options to add a sub:
- Use a powered sub that has pre-amp inputs, and connect the pre-amp outputs from the amp to the pre-amp inputs on the sub
- Use a powered sub that has speaker-level inputs and outputs, connect the amp's speaker outputs to the sub's speaker inputs, then connect the sub's speaker outputs to the speakers
There are other ways to do it. For example, if your computer has outputs for the front left/right audio and the subwoofer audio, you can utilize that - but it makes volume control a bit more complicated.
Please let us know if you have any questions about how to do any of that.