So ...

We are going to use a handy plugin called Visual icon Fonts.

Here it is:

https://wordpress.org/plugins/wp-visual-icon-fonts/

It's a medium-size plugin (634 KB), so let's see the usual speed tests ...

Here are my results before installing the plugin ...

... and the result after installing and activating the plugin:

No more comments needed ...

So, let's see how it works ...