You can connect to FTP/SFTP/FTPS folders in one of two ways: 

1. through the Trados automation (or 'hot folder') module, which lets the system pull in content from an FTP/SFTP/FTPS folder to create a translation project, and return translated content to the same folder. 
2. through an easy-to-deploy pull connector that lets users of the Trados customer portal select content assets from an FTP/SFTP/FTPS folder when creating a translation project. Assets are pulled into the Trados project for translation, and once translation is complete they're available through the customer portal for upload directly back to the relevant folder.