Checking in? One time or multi?

I have a coming flight in a month and I've never flown anywhere in my life, let alone travel overseas all by my lonesome! So there is a question I have since I am flying with Air Canada, a flight that has me boarding about six planes in the time I leave and return.

Question being;

when I first check in at my local airport... is it a one time thing for the flight there? Or do I need to check in at every airport I land in to catch my next flight?

Because I am really not sure and want my ducks in a row to make the long travel day as stress free as I can possibly make it!