Does anyone know how much a Junior (U23) Rider should train and how?. Also, does anyone know of any online guides for Junior training?.

Pretty much like an adult, unless you're too young to feel safe on the roads...

EDIT: Some more advice. Go for a rides before school on nice days if you have a free block. Ride your bike to school if you can, it's a good way to keep the legs snappy if you're too busy to ride after school. As I said, any adult training program will basically work for a junior if you have time and the means. Pick up a training book, such as The Cyclists Training Bible by Joe Friel, although I find some of the material daunting for someone who does not, or is new to, HR/Power training.

The best advice I can give is remember why you started to ride - because you love it. Put any delusions of grandeur in the back of your mind, and just go ride.

By the way, I am a junior.

U23 is not the same as junior

"Seenyas to the line. Chewnyas on deck".

I hear people say they train 7-20 hours a week, while the training bible says for most weeks no more than 8. Whats up with that?

Training varies, depending on your current experience/fitness/ability and your goals and your age (if your U17, your still growing meaning that a high workload may be more harmful than good). If not already, you should get restricted gears not only to comply with the rules of junior racing, but it also promotes high cadence and reduces stress to joints.