For installing fonts in Windows 10, it's best to head for the Control Panel (Start Menu > Windows System > Control Panel) and look for Appearance and Personalization. The fonts section is in there.

Most Microsoft apps use the same font by default. However, if you want to always use a different font in one or all of your desktop 365 apps, you can change the default manually.

Since the last update, Microsoft Word uses Aptos instead of Calibri as the default font. If you don't like this font, you can easily switch to Calibri or another font.