If you purchased TurboTax download you will go to the following link to download your software. If you purchased TurboTax Online- then you would need to go to turbotax.ca/activate and once activated sign into your TurboTax Online account- then choose the software you purchased- complete your return and just before you file, it will ask you to pay- on that payment page enter your code under coupon code.
Thank you for choosing TurboTax.