Go to the Configure Site > Languages/Configs menu tab to manage and add more Languages/Configurations to your website.
This will take you to the list of Languages / Configurations in your website, by default English:
To edit a specific Language/Configuration, click on each of the Edit Configuration icons. You can also choose the Language/Configuration from the menu on the top of each setup/configuration admin panel page:
Click on the Add Language/Config tab on the top right of the Languages/Configs list page to add a new Language/Config.
You can add an Icon, which can be used in the Languages/Configs Menu you display for your website visitors to choose their Language. Choose an Abbreviation for the Language/Config to denote that webpages with this suffix is in this Language/Config. For example, for the default language English, you would leave this blank. For Spanish, you would choose "spa", for example, denoting that webpages with the suffix "_spa" are in Spanish. This can be useful when the website visitor switches Languages. If the page they are on has a compatible webpage, they will be redirected to that page - i.e. page goes to page_spa if available. Otherwise, they will be redirected to the first position page of that language.
You can choose to populate your new language/config fields from another one, to save time and be easier. Then you just go in and edit the necessary fields.