Want to add Field Conditions to an existing pdf form

Hi there

I am trying to add field conditions to an existing pdf but I can't find the way to get onto the 'Yellow' text boxes so i can change them.

I have tried through edit form and prepare form but i just get the white boxes which don't allow the form field changes.

Can someone please explain how i get to the for to make permanent conditions please, the link shows the yellow boxes but i don't know how to get there!  https://helpx.adobe.com/uk/sign/using/form-field-conditions-settings.html