Unfortunately, there is no button to change the language on Turbotax.
You would have to log out and on the top right corner, you would be able to see the language switch button or simply follow the following link TurboImpôt.
Thank you for using TurboTax.
TurboTax Expert Assist
Get answers to all your tax questions
Our experts are available on-demand, no appointment needed. Get help all year long with TurboTax Expert Assist.