How to change font family default setting in dawn theme

[amisha-29]

in my dawn theme currently the font is assistant and in the code it is showing assistant_n4 default. I want to use this font-family: Overpass, sans-serif as a default  but there is no font in the search option. How can i add this as a default font-family. Also I'm not getting the code from where all the fonts are coming. Please help me