The rules of hockey are set by FIH (International Hockey Federation). The rules are available online here.

You may also want to try watching some YouTube videos which are available to explain the rules.

It's definitely a good idea to have an awareness of the basic rules. These are easy to pick up pretty quickly. Beyond that, most people tend to learn most of the rules as they go along. Even experienced players don't know the more obscure rules of the games!

If you are unsure about a rule, please feel free to ask. Asking an umpire after a game is often a good option.