Each of your new brakes will have two wires for the brake magnet. One wire is for 12-volt power to the brake magnets, and the other wire should be grounded either to the trailer frame or to the main trailer ground wire. It does not matter which wire is used for power or ground because they are not polarized.
If you have any questions about this, please feel free to reach out to us via phone at (833) 416-9396 or email us at support@thetrailerpartsoutlet.com and we would be more than happy to help!