Hi @gerah,
First, specify the return value for the file field as the ‘File URL’ from the field group edit screen, then use then use the following code on the front-end to create a download link for the uploaded file:
<a href="<?php the_field('field_name'); ?>" >Download File</a>
For more information on this, have a look at: http://www.advancedcustomfields.com/resources/file/
