Setup

First, enable PWM and set up your PWM channels in 2_Boards.ino

Scroll down to this part:

//------------------------------
//---------PWM CONTROL----------
//------------------------------
#define PWMENABLED 0

#if (ROW6_PWMCOUNT > 0)
  int8_t PWMChannelPins [ROW6_PWMCOUNT];
#elif (PWMENABLED == 1)
  int8_t PWMChannelPins [] = {99};
#endif

Set PWMENABLED to 1 and add your microcontroller pins used for PWM to create PWM channels.

In this case we're using pins 16, 17 and 18, they will be on PWM channels 1, 2 and 3, respectively:

//------------------------------
//---------PWM CONTROL----------
//------------------------------
#define PWMENABLED 1

#if (ROW6_PWMCOUNT > 0)
  int8_t PWMChannelPins [ROW6_PWMCOUNT];
#elif (PWMENABLED == 1)
  int8_t PWMChannelPins [] = {16, 17, 18};
#endif

Don't mind the ROW6_PWMCOUNT stuff, it is related to an automatic PWM setup for the CB1 board.