Changing CSS font styles

hi,

i’m having huge problems trying to edit fonts.
i am using the google fonts plug-in and want to use Source Sans pro throughout the site which i have set within the GF settings – but it’s not working.

strange thing is it WAS working here & there if i refreshed – so i’m thinking maybe there is a clash somewhere?

do i also need to put the changes in the quick css editor?

i need to do things like change the font weights – i don’t want headings to be bold.
also – i need this to work in the sliders – this font isn’t cooperating.

please help…

thanks

jaz