How operate servo using PCA9685

Hi guys! I hope all are good.
how to control a servo with PCA9685, using PX4 autopilot. I am searching for a user manual, but up to now, I did not get any answers. Please give any suggestions on this. I have 8 pins PWM pins are there, in these 6 pins are used for hexacopter. 2 free servo pins are free, but they’re not getting any signals. My drone is IF1000. reference

Thank you in advance