It means you should choose which languages should be translated via gtranslate. In this case you will need to install GTranslate general version and make changes in the gtranslate .htaccess rules and set the language codes.
You cannot translate the part of the page via gtranslate and another part via joomla language manager.
To edit the translations you will need to add ?language_edit=1 to the end of the URL and you will see editing tools in frontend. Here is the screenshot