If you wish to change the default language of your website from English to French, you can follow this FAQ on how to do so.
1) Once you've logged into the website editor, on the left hand side bar select the "WPML" option near the bottom of the side bar
2) After you've clicked "WPML" in the "Site Languages" box select "Change Default Language"
3) From here, select "French" and click "Save"
You are now done and your websites default language is now French