Changing the fonts

Hi,
I would like to change the fonts of my website.
I go in the Template Setup, in the section "Fonts" and I modify the fonts of the header for example, using Google fonts. I copy the link, and I copy the Font family.
After Saving it, I can't see any difference on my website. I tried to flush the cache... but no change.
Can you help me with it and tell me how to apply the changes?
Thanks a lot for your help.

Could you please post an url to your site?
Could you also post a screenshot of current font settings?