Hi Nigel,
More knowledgeable people will be able to give more detail but basically you need to have 1 brushless ESC for each brushless motor, in your case 2 ESC’s and 2 motors.
They can be connected to the same receiver channel with a ‘Y’ cable if desired. To reverse direction of spin simply swap 2 of the 3 wires between ESC and motor.
When using 2 ESC’s you should remove the +ve wire from one ESC to prevent them both trying to provide power to the receiver.
Dave