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.