Hide/Show/Disable Element when fields are empty

I am new to the plugin and am trying to understand how the conditional logic works.
One area I cannot figure out is how to hide/show/disable an element if another element is not filled out.
Example, I want to disable a “Next Page” button unless certain fields are filled out such as First and Last Name
So on the Next button I put a if <First Name> is < > (where I leave the condition field empty, I assumed this would work to disable the Next button but it does not.
How do I set up a condition that says if X field is not filled in, checked, selected or otherwise filled out, then disable/hide/show this element?
Thanks in advance.

https://ww.wp.xz.cn/plugins/caldera-forms/