Files keeps the pictures, videos and documents you use in your posts.

• Upload: click Choose files or drag them in. You can also import from Google Drive, Dropbox or OneDrive when available.
• Organise: create folders with Create Folder.
• Edit pictures: crop to 1:1 square, 4:5 portrait or 16:9 landscape, adjust brightness and contrast, apply filters, and add simple text.
• Use in posts: in the composer, choose Select media to attach files from the library.

Your plan sets how much space you have and the maximum file size.