How do I troubleshoot this margin error on my form?

I am trying to modify a form and give it a theme. The theme looks fine and dandy (seen on the left) in the Designer and on the Form Builder, but once I preview/see it live (seen on the right), the right side of the form is going off the page.

I've tried changing the horizontal padding, but nothing seems to work. 

Thanks, 

Dani

What is the URL of the form you are referring to? Here is an example of how to get it:

Reply back with direct link of the form, so we can check further, we will be glad to assist you.