In order to test return-home, takeoff in manual mode with MODE_CHANNEL set to magnet home (HIGH).
At safe altitude (20m min) enable the autopilot.
Observe as the UAV is circling while gaining altitude.
Should anything be mistuned, you would be able to spot it while the UAV is overhead (be ready to take manual control by disabling autopilot at this stage). You also make sure that emergency return home is functional.
Once the RETHOME_MIN_AGL is achieved, you can hear lowering motor throttle. Move MODE_CHANNEL slider to low position (enabling normal navigation) in order to start mission execution.