Great question. I want to make sure you're able to use the program in your preferred language. I'll give you the steps you need and let you know a bit more about what happens when you make the change. Changing your language in QuickBooks Online just takes a few quick steps, which you can follow below while logged in using a browser or the QuickBooks Online desktop app for Windows/Mac.
One thing to keep in mind about making this change is that it may cause some language abnormalities, meaning that some areas of the product may appear in French while others appear in English. There isn't currently a way to correct this, but it's something we're aware of and working on. If you're hoping to have a fully French account, I recommend creating a brand new account instead. Here's a link to the French portion of the plans on our website: Prix et forfaits. If you do create a brand new French account, don't forget to cancel your current subscription so that you won't be charged twice. A new account would also mean starting fresh since data can't be migrated from one account to another.
If you're simply hoping to send invoices to your customers in other languages, that feature is now available in the product! Read our page about How to send QuickBooks invoices in other languages to learn more.
I hope that helps. I'm here if you've further questions. Have a great weekend!