I believe this has nothing to do with ACF.
Some googling will surely give you the answers how to show tags with custom post type.
Like… http://wordpress.stackexchange.com/questions/59583/list-all-the-tags-from-a-custom-post-type
or… http://wordpress.org/support/topic/list-tags-from-custom-post-type
Hopefully you can figure it out!
