I just started doing this - I'm sure others can chime in with more complex setups, but this works for me. FWIW, I use the SA MIDI Adapter, but it should work fine with the Neuro Hub too.
- Enter the Control Center on the HX Stomp
- Select one of the lightning bolt icons (one-time events that are fired when that patch and/or Snapshot is selected)
- Scroll the left encoder until you see MIDI options
- In my main patch, I use two lightning bolts per Snapshot - one sends the desired on/off state to the C4 using MIDI CC 102 (check [Invalid or Expired Link Removed] for other CC values) and the second sends a PC message with a slight delay (I think 50ms) to change presets on the C4 as needed
- Now test it and see if it did the right thing

- FWIW, I had to fiddle with the delay timing when I was both changing presets and turning on/off
In the HX Control Center, you can also have expression pedal(s) or unused stomp buttons send MIDI messages, e.g. if you wanted to hook an expression pedal up to the Filter cutoff frequency on the C4.
Hope that helps get you started - I'm not at my board at the moment, so this is from memory, but it's pretty straightforward once you know where to look in the Control Center. Have fun!