BB-RELAY-4PORT overlay

Hi folks,
Having a brain fade moment I think.

I'm interested utilising in the BB-RELAY-4PORT overlay, so I've loaded it up.

# cat /sys/devices/platform/bone_capemgr/slots
  0: PF---- -1
  1: PF---- -1
  2: PF---- -1
  3: PF---- -1
  9: P-O-L- 0 Override Board Name,00A0,Override Manuf,BB-RELAY-4PORT

Thing is, I was kind of expecting the GPIO pins to become available similar if I had "echo PIN_NUMBER > /sys/class/gpio/export"

But that doesn't seem to be the case. There's nothing there.

# ls /sys/class/gpio/
export gpiochip0 gpiochip32 gpiochip64 gpiochip96 unexport

What (apart from a clue) am I missing? Does the overlay merely configure the hardware for exclusive use and I still have to initialise via C/C++/Bash etc. (ie, Linux itself doesn't pick up the hardware config and do this for me)?

Thanks in advance,