Start off with 2lb ankle weights. When you can finish the workout on three separate occasions, you can try 5lbs on each leg. Proceed in this manner (+2 and 1/2 pounds per leg) every three successes, until you are at 20 lbs per leg.
I just want to say: This WILL take a long, long time, but if you work hard, train diligently, and get adequate rest, a few years from now you may be at the super advanced level or even adding the ankle weights.
Good luck and train hard!