Font Manager question

Hi!
I try to use the google font i use on the site to the Visual Ccomposer Betterweather widget.
I understand that i may set up one web safe css stack. But there are several stacks here and i have no idea how i may set up which stack to use.

I can’t find any explanation how to set up my personal font. For example, if i set up one stack with ‘Lora’, serif how to force this font stack?
Thanks.