Most first-time filers can't use NETFILE, they need to print and mail their returns to file. If you are using TurboTax Online, select File > Filing Hub* from the left side menu. Then click on "Print & Mail your return(s)" to go to a page where you can download a special version of your return to print off and mail.
*If you don’t see the Filing Hub option under File, then select CRA Online Mail and continue forward from there to get to the Filing Hub.
This CRA webpage has a list of where you can mail your return: https://www.canada.ca/en/revenue-agency/corporate/contact-information/where-mail-your-paper-t1-return.html