If you have his return in a .tt17 file, then you can import it into either a TurboTax Online Or TurboTax CD/Download return for 2018. If he used TurboTax Online last year, you would have to use the same account he used last year to be able to import his 2017 return.
Here is how to transfer information from your previous year's tax return in TurboTax CD/Download: https://turbotax.community.intuit.ca/replies/2647740
Here is how to transfer information (personal details, carry forward amounts, etc.) from your previous year's tax return in In TurboTax Online: https://turbotax.community.intuit.ca/replies/2647786