The shows are free to the public and you pay an entry fee of about 50p to enter your hamster in pets. You take him in his cage or a safe carrying box and when you get there you ask the secretary to enter him in pets. They will show you where to put is cage and give you a sticker. He will be judged on tameness and condition not on his type colour etc as in the main show. Hopefully you will win a place
You can chat to all the showers and ask their opinion of your hammie and what is looked for in a show hammy. They need to conform to certain standards and be certain colours so you can ask then decide if you would like to show in main show next time.
I would say enter pets first show so you can see what happens then decide. I am sure you will enjoy it and look forward to hearing how he gets on. I think Holly has a guide to showing on her website.