You should be ready for the physical before you apply, but if you're not then really train to get ready for it. You can and can't do whenever you want to, but in the end you do it not long after or during the other testing and interviews. As for your present job, you'll have to stay in for a bit longer at least. Even if you dropped off your application package off tomorrow it would be at least a few months before you would be in. There is even a possibility that it would be next year before you could get in, but if you really want to be in the Canadian Armed Forces then it is definitely worth the wait.