Media and files are managed in media libraries that are specific to each type: images (JPG, GIF, and PNG), video (YouTube or Vimeo), audio (SoundCloud), and files (PDF, DOC, PPT, etc.). The media library allows you to browse for existing media items that have been previously uploaded to the library, or add new media items.
Please see the following how-tos to learn how to manage and create media items for use on your website: