Thanks for bringing this up. A little mystified why they don’t cover this in the Picade kit docs. The instructions just abruptly ends shortly after assembling hardware and running curl https://get.pimoroni.com/picadehat | bash and says, “…have fun!”
I had to delete my old ~/.emulationstation/es_input.cfg file and try again. Thanks to that tip from Picade Hat joystick not detected w/out usb keyboard plugged in