you can use the "high-level," inputs.on the subwoofer buy running speaker wire from the speaker in the bottom of the cabinet to the "high-level," inputs. on the sub

In spite of the name, a ‘subwoofer out’ isn’t the best way to connect a subwoofer to a quality music system. The preferred method works even if a preamp doesn’t have special subwoofer or preamp outputs, however, you do need a subwoofer that can accept a “high level” (also called “speaker level”) input. With this method, the subwoofer connects to the back of your amp exactly where you plug in your speakers.Don’t worry, the subwoofer will not draw power from your amp. An active subwoofer presents a very high impedance load, so the amp doesn’t work any harder when you connect one, two, or even a line-array of six subs to it. The sub is just seeing a signal and amplifying it.
hear is link
https://www.upscaleaudio.com/pages/subwoofer-tips