What do you want to do, Colleen? Prepaid or postpaid?
In either case you'd need to buy a SIM card (prepaid one is $20, postpaid $10 from Koodo) and then activate it.
Prepaid can be done entirely online, there is no credit check etc, just buy the SIM and activate it...
Postpaid needs a few more steps and a credit check, so you might be best off to visit a store to have the personnel set it up for you :)