Your odds of 'joining in 3 months' are not necessarily that great. 2nd Irish is part of 33 Brigade. The brigade's next basic military qualification course starts in early October. If you join mid summer you may not be processed as a recruit in time, and you may find that all fall BMQ spots have been taken by those hired in the April- June time frame. I would advise contacting the unit's recruiter mid April once they get their hiring allocation for the new budget year, and confirming what they think is best in terms of your application. I can say with certainty that you will not be in a position to train until at least early fall, and that's assuming your application goes through quickly enough.
If you get in in time for the fall BMQ, you would then do your two month Infantry course in the summer of 2013, leaving you infantry qualified by about July or August next year. From there you can be used within the unit as a soldier in a rifle platoon starting fall 2013.
My advice is contact a recruiter as soon as possible and figure out how early you can get your name in the hat. Find out if they have spots for hiring (but don't expect a firm answer on this til middle of next month), and ask at that time if they have already filled their expected BMQ loading for next fall. Spots are limited.
Get yourself in good physical shape. Learn as much as you can about what the infantry does, how, why when and where; what the 2nd Irish have contributed to the forces, what the role of the reserves are in Canada, and what the Canadian Forces does at home and abroad.
Read thoroughly through the recruiting forum on the site. Most questions have already been asked and there's little patience here for those who aren't able to do their own research and search for information.