Dryer: old knob pulls out, and new knob is placed on, no more complicated than that!
Washer: old knob would just spin and not engage for cycle selection. To remove, pull back until you see a plastic u-shaped clip, acting as a pin. Remove the U clip (I pushed with a chopstick but needle-nosed pliers would be good), knob slides off. New knob slides right in.
Both together took about :03 total.