Yes, it is possible for an author to submit the metadata for an article in more than one language. In the language section of the Journal Management pages, you must first make sure that the "Forms" and "Submissions" boxes checked for all of the languages you'd like to allow for submissions. If that is completed, when an author submits a manuscript, once they reach Step 3. Entering the Submission's Metadata, they will see a dropdown menu for the language of the metadata they wish to enter. They will have already selected the primary language of the article in Step 1, so that loads as the default for that page. However, after entering the primary language information, they can flip to other languages in the list and enter the translations. If you're asking authors to upload entire manuscript files of translations, I'd suggest instructing them in your author guidelines to upload any translations as supplemental files or including all of the translated versions in the main file document.