Could you read through that and see if you follow it okay? (Since writing that, you can now add your custom code at Toolset > Settings > Custom code, no need to edit your theme's functions.php file or use the Code Snippets plugin.)
I nearly missed your reply, as the thread had already been marked as resolved.
Do you still need assistance?
Let me set up a private reply so that I can access the backend of your site to see how you have things set up.
You may want to create a temporary admin user for me to use that you can later delete. And be sure to have a current backup of your site, even though I don't intend to make any changes.
What is the custom post type that has the image fields?
What template or layout are you using to display the posts with slider?