Locate the vehicle end of the trailer plug wiring, tap in to the smaller of the 2 black wires for your positive feed to the buzzer making sure to install the fuse.

Negative ring terminal bolts to the chassis in the shown location. 

Bolt the squawker to the lower wellside support panel using M8x20 button heads with a flat washer and nyloc. 

Hook the trailer plug back on the retainer clip. 

Test that the squeaker works when in reverse. Your BYD squawker installation is complete.