1. Start out by logging into cPanel
2. Click the File Manager icon
3. Navigate to the location of your WordPress install, in most cases it will be located in the 'public_html' folder.
4. After double clicking the public_html folder, look for the file named: wp-config.php. Once found, right click it and click Edit.
5. Once inside the Editor, simple place the following line below the PHP open tag:
define( 'WP_AUTO_UPDATE_CORE', false );
It will look like this:
6. Click Save Changes at the top right. Your WordPress install will no longer update automatically.