On the back of the Foxsat there are 3 connections. To use both tuners on a single cable you need a short length of coax with as f connector on each end. You simply connect the middle connection tuner 1 out to tuner 2 in.
You won’t get the capability to record any two channels at the same time but it will make a big difference as to what you can record and also what 3rd channels are viewable by recording two.