How to change the fonts used in Gnome 3?
The default configuration tool of gnome does not provide an option to change the fonts. However, the
gnome-tweak-tool provides it.
If you have not installed it, you need to install it first. On Fedora, run
# yum install gnome-tweak-tool.
Then you can run
gnome-tweak-tool and set the fonts as in the following figure which is clear by itself.