Field hockey is governed by the FIH. Field Hockey Canada uses the same rules at all levels, with slight variations depending on the level of play and league rules.
This link to the FIH website will direct you to the latest outdoor and indoor field hockey rules.
The FIH umpires briefings are also very useful in learning how to interpret and apply the rules. They have also set up a video library where you can watch international umpires apply the rules, with explanation and commentary.
Umpiring is a skill attained through lots of experience, but getting help and advice from a more experienced umpire can often help in improving those skills a little bit faster. Feel free to contact us at firstname.lastname@example.org if you would like to receive umpire mentoring.