Installing fonts in Microsoft office on windows office is very simple process, follow below mentioned steps.
Download required front from internet.
You can download font from any of the following location ( Please check copyrights on below sites, these are shared for reference only. I am not aware of copyright and user licensing at below locations,).
http://www.marathimati.com/downloads/marathi-fonts
http://devanagarifonts.net/marathifonts.html
http://marathi.indiatyping.com/index.php/download-marathi-font
got to Control Panel --> Appearance and Personalization --> Fonts
or simple type fonts in Cortana search box and it will take you to required folder.
To install newly downloaded font, simple drag *.ttf file and it will install the required font.
post by Pravin