Bayes' Theory

Hi i'm currently working on a horse race prediction project and trying to include bayes' theory in my project. The thoery is new to me I am trying to mould the equation so I can fit in the horse probability of winning a race i.e 1/10 if their are ten horses given that the horses rating (gained from adding together its speed rating and jockey rating etc) is higher than the other horses. I am just stuggling to try and mould bayes theory to fit this into it.
Any help on how this could potentially work would be greatly apprciated!

Why not to read some books about it.
It's too much about Bayes.
First, you need pre-prediction-probability,then mix the real data to adjust your
prediction probability(post-prediction-probability).