This TurboTax Canada FAQ tells you how adjust a NETFILEd return using ReFile: https://turbotax.community.intuit.ca/turbotax-support/en-ca/help-article/accounting-bookkeeping/file... ReFile is not available for TurboTax Online 2021 or earlier, or TurboTax Desktop 2019 or earlier.

This Canada Revenue Agency (CRA) web page lists other ways to can adjust your return: https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/change...