When you save the page you will see at the bottom of the page a list of already present links to other languages. If your language is not already present (or if there is but the link is not correct) click on the ''' +/-''' links to automatically edit the correct template. You have to insert the correct link to your language version in the template just opened. This change will automatically reflects on all pages of all language that use this method (you will may have to refresh the page to see the effect of this change)