The error means the file you're uploading is bigger than PHP's limit (upload_max_filesize). The fix is to raise the limit from your control panel.

The fix

• cPanel: Software → Select PHP Version → Switch to PHP options, or MultiPHP INI Editor. See cPanel: PHP version and settings.
• Plesk: Websites & Domains → PHP. See Plesk: PHP version and settings.

Raise them together:

• upload_max_filesize: e.g. 128M.
• post_max_size: slightly higher, e.g. 130M.
• For very large files or imports, also memory_limit and max_execution_time.

Then in WordPress go to Media → Add New: the maximum size shown there should have changed.

If it doesn't change

• Some values may be capped by your package. Open a support ticket with the value you need.
• For very large files (e.g. videos), it's easier to upload them with FTP.