The black knobs are the compression adjusters.
If you are positioned so you are looking at the top of the knob (facing downward for the forks, or facing the knob on the side of the shock), if you turn the knob clockwise you increase the compression damping.
The knobs are also labeled Hard and Soft.
The standard (base) settings from the factory are:
Front forks: Compression knob rotated clockwise until it lightly bottoms, then counter-clockwise 12 clicks.
Rear shock: Compression knob rotated clockwise until it lightly bottoms, then counter-clockwise 10 clicks.
Adjust the damping at each end to you desired settings.
Be sure both front adjusters are set to the same settings.