How to change fonts in body?

Hi,

What should I do to change the fonts which are used mainly in body (post, pages, sidebares)? Main problem here’s that the native (polish) characters don’t work on site and wordpress is simply changes font in to other. I’ve tried some of the solutions, but I couldn’t find required in those hints, code. I know that temptation’s using Awesome font, but it seemes there’re other font it’s using in body.