How to add custom fonts via Child Theme?

I want to add custom font to font selectors. I haven’t found a filter.

I use a plugin called Custom Fonts by Brainstorm Force.

The only downfall is the font isn’t added to the selector, you have to type it in manually each time you use it.

I add my fonts myself using my child theme, without a plugin.

My request is all about not typing manually the font names.