Hello,
If you have purchased TurboTax Desktop CD; then the key should be on the sleeve that the CD was in.
If not and you need help regarding the key; please go through the following link :
http://support.intuit.ca/turbotax/en-ca/iq/Install-TurboTax/I-don-t-have-my-installation-key-code--H...
Hope this helps.