Single post in Guide to CSS (Beginner & Intermediate) [In Progress]

I know there's a way to do it as I've done it before but I can't for the life of me remember how. But can someone give me a hand on using fonts that you've uploaded somewhere like onedrive so you link it directly in a template for use? Id used it in a template before but of course the thread I know I used it in has long since been deleted