If you want the viewer of a branded portal to have the ability to switch between English and French in one click, follow these steps.
Publishing your portals
1. Create two portals, one in English and one in French with the same content. Remember that you can save some time by copying the portal.
2. Publish the portals and make sure to copy the links.
3. Go back to one of the portals to edit it. At the top right corner, chose the default language (the language that the viewer will see first)
4. Enable Multi-Language.
5. Click on Configure, paste the link to the other portal, and click on Save.
6. View the branded portal and switch between the two languages to make sure everything is working properly. You should now be able to change between the two.