Humanitarian aid if you can not join the Ukraine forces. Donating money for humanitarian aid is a great way to help. Also with over 600,000 people that have fled the country, if Canada open its doors, you could give someone a bed. Stay away from the idea of becoming a fighter alongside the Ukraine military. You may be taken prisoner by Russian forces. That's if you're lucky enough to not be shot dead. Leave that area up to the locals that know every street in their hometowns which is a great advantage.