Schwinn IC4 pictured. Functionality is the same, but your bike may vary slightly.
Loosen and remove the screws from the fender (circled white), taking care to hold the fender to prevent it from dropping.
(Reference 4)
Schwinn IC4 pictured. Functionality is the same, but your bike may vary slightly.
Watch the collar (circled red, middle) and resistance nut (red arrow, bottom) for movement while rotating the adjustment knob.
(Reference 5)