Please find below the wiring diagram in order to correctly use the Driver Servo - PCA9685 16' with the I2C. You also need to power up the board and raspberry with a 5v and at least 3A (They can share the same input voltage)

Simple code example to set all 8 servo to the angle 50° (note that the angle need to be: 0 < angle < 180)

from adafruit_servokit import ServoKit

kit = ServoKit(channels=16)

for i in range(0, 7):
        kit.servo[i].angle = 50