Custom field passed to iframe

I am using a user frontend plugin so that users can submit posts without having to access the dashboard,

They will be supplying information that when submitted will be submitted as custom fields.

What I want to do is pass the values of the custom fields into an iframe address with a page I have developed.

I presume that the code will be placed into the single.php page but i’m not sure of how i would go about coding it.

Any help would be much appreciated,

Regards