I just saw in another thread that you're 16 years old, not 20 like your profile says. That changes my advice quite a bit.
I suggest starting with a bodyweight routine that's still much better-designed that what you've been doing. I prefer younger guys build a base with basic full-body bodyweight stuff before advancing to free weights because it builds strength, muscle, endurance, balance, and can help to prevent injuries.
3 Days a Week
A) Squat 2x12-15 (feet flat on the ground through each rep)
B) Push-up 2x12-15 (legs straight, never knees on the floor. Elevate hands if needed)
C) Alternating lunge 2x10-15 per leg
D) Neutral-grip pull-up (assisted if needed) or horizontal "fat-man" row 2x12-15
E) Plank 2x15-count
F) Burpee 2x12-15 (4-count movement. No jump needed.)
As soon as that's easy from start to finish, move right into the Waterbury program. Just my two cents.
Pretty sure he's referring to bicycle crunches, alternating right knee to left elbow-left knee to right elbow.