There may be other ways of doing this, but here is what worked for me. This is on a Mac.
1) Go to System Preferences / Bluetooth
2) Connect/Pair with your device (if you haven’t already). You only need to do this step once, just so the computer has the pedal in paired with it and will remember it.
3) Go to H9 Control. If it says it doesn’t detect a pedal, select one manually off of the ones you just connected to.
4) The easiest part – the software is a little misleading IMO – after you have connected with one pedal, go up to the menu bar, click Devices/Connect Device Via Bluetooth. (*This was the misleading part for me, as I assumed that meant it would disconnect from the current device. It doesn’t).
5) When that menu comes up, select another one of your H9’s that have been paired with the computer. In the presets where you can see your computer, you’ll now be able to see all the H9’s that are connected.
Hope that helps!