1. Visit and download the android app “MIUI Custom Font Installer” from Google Playstore… Now, select your favorite fonts from the web, only TTF and MTZ formats are supported for now. You are responsible of all Fonts Copyrights, I prefer free fonts.
2. Place the font files (TTF or MTZ) on a folder you can remember. I created a Fonts folder for keeping all fonts in one place. Now, open the MIUI Custom Font app installed earlier. Go to the Local Screen (see snapshot below).
3. Find and Open your favourite font file using the browser icon bottom-right. Select SET. Select Method 3 latest. Select OK on the Notes screen.
4. Select the third option with brackets (Apply Me). Now restart phone if needed.
5. VOILA !!
TIP: The attached Post Image resembles my current favourite font (Search for Caviar Dreams) Using it for its style and legibility.. . Happy Font Changing <3
Disclaimer: I do not own the given link above and do not take responsibility for any actions and/or reactions you partake using your phone and/or online fonts.