Good day @optimium,
Depends on how you want to control them and what exactly you want to achieve, but I'd say this should be of help. You'll need to know exactly how your motors work though.
In the provided example, to output PWM signal (the pinouts in the back) you just need to know which one you want to output to (from right to left starting at 0, the example uses the first and third pinouts) and the output you want. This'll vary on the type of motor you are using, you should be able to take the steering (just under the
# Abstract the direction of the Rover comment) as an example for servomotors. The value you pass through to the servo will set it's rotation/position.
BTW this is all assuming your motors are compatible with the ErleBrain 3.