How to install hindi font in kindle 6.4.5 without rooting it?

Question

I have Kindle whose version # is 6.4.5. I have installed whatsapp in it. But the Hindi messages will not appear correctly , it will be shown in rectangle form. I have tried to install hindi font as mentioned below

Before installing fonts you need to make sure that those fonts meet the minimum requirements, such as:

      a. The format used is TrueType or OpenType. 
      b. You need to have 4 variants of the files: regular, bold, bold 
          italic, italic 
      c. The file structure should look like this: [name]-Regular.ttf , 
          [name]-Bold.ttf ,[name]-Italic.ttf, [name]-BoldItalic.ttf 

After you make sure they meet these requirements you need to take the following steps in order to use your custom fonts:

1. Connect the Kindle to your PC;
2. Use the computer and browse the content of the Kindle and create a folder in the root of the drive : fonts;
3. Copy your files in that folder, following the structure given above;
4. Start Calibre and go to Kindle Configuration > Modify Kindle Settings;
5. From the Font Family, choose the fonts you need;
6. Save the settings and wait for the device to reboot.

But get no success.. Please can any one help me