Gimbal setup on pixhawk

when setting up pixhawk FC with px4 firmware , I’m setting up DIY s500 frame with a BCG gimbal, in the set up process there is no reference to setting a gimbal , how is gimbal setup actions activated in QGC

thanks
Tony

FYI @olliw

What is the interface of your gimbal?
Have a look at these params: https://dev.px4.io/v1.9.0/en/advanced/parameter_reference.html#mount