There is info here on what happens at a show:
Shows and Displays - National Hamster Council
All hamsters are judged against a set standard set by the National Hamster Council in the UK. These can be found here:
NHC Exhibition Standards - Syrian - National Hamster Council
If you post a picture we can guide you on what classes to enter though it is always nice for a new person to enter the pet class at their first show while they get a feel for what is involved.