Are you meaning for your end user to download a file? If you use URL as the field type, it will take you to the url. By using the File field type, you can select ‘File URL’ as the return value and then on the php page use:
<?php
$file = get_field('download');
if( $file ): ?>
<a href="<?php echo $file['url']; ?>"><?php echo $file['filename']; ?></a>
<?php endif; ?>
to grab the value on the front end. Then when the link is clicked, the download will be done automatically.
