How can I change the base font style using CSS?

Question

I want the font to be a sans-serif font like Calibri.

Answer 1

To change the base font of the entire application you would add the following CSS.

body, .ui-widget {
    font-family: Calibri, sans-serif !important;
}

This CSS should be added to a custom CSS file. Adding a custom CSS file is described in: Where should I add Custom CSS.

The best way to play around with the CSS is in the Browser Developer Tools area.

A good YouTube video that describes that process is  https://www.youtube.com/watch?v=25R1Jl5P7Mw