Font formatting On ADD or EDIT form

New to knack and wondering how can I format a field's font on an ADD form? It appears you can only change font size/bold/etc on a details form. I have a simple ADD form with an equation field that adds up some values being entered. I simply want to make that equation field larger and BOLD on the form but see no way to do that? I am assuming I need to use script or code but don't have any experience to do that. 

A related question is to make that same field backcolor red if the value is not 0. 

I love knack but sometimes struggle with these basic elements of page design and why available in some areas but not others. 

Any help would be appreciated!