If you need to upload big files to your application, you will need to tweak some PHP settings, by default the max_upload_size option is 2MB and post_max_size is 8MB.
To update these options, you need follow these steps:
Log into your cPanel account
Go to the "Select PHP Version" module
Click on the "Switch to PHP Options" link
On that page, you will want to update both max_upload_size and post_max_size to fit your needs.
Be advised that uploading very big files using PHP means having a single PHP script running for a long time (for each upload), this means having one entry process running (for each upload), reducing the number of concurrent visitors your site can handle, use this option with caution.