Where /how do I enter the registration number when I already bought Turbo tax at Best Buy ?

Here is how to use a prepayment or activation code in TurboTax Online: https://turbotax.community.intuit.ca/replies/2648021

If you are using TurboTax CD/download edition, it will ask for your installation key when you install the program.

I bought Turbotax at bestbuy but when I enter the code with the letter and number it say wrong .What can I do

It wont go . It say something wrong