Unfortunately, if you used TurboTax CD/Download last year and no longer have the return files, then you will have to start your 2018 return from scratch. You 2017 Notice Of Assessment should have amounts like tuition carry-forwards, etc. You can also use the CRA My Account service to see the information on your 2017 return. https://www.canada.ca/en/revenue-agency/services/e-services/e-services-individuals/account-individua...
I have a new computer. where to copy my 2017 return so I can retrieve the information for my 2018 tax return?
You can put it wherever it’s easy for you to find. When you do File>Transfer 2017 Return, it will allow you to open the file from anywhere. If you prefer, you can put it into your documents where TurboTax would put it, which would be something like: C:\Users\yourname\Documents\TurboTax\2017