To install Malayalam fonts, you first need to download the font file. To do this, you can use Google in order to find a download website. For Windows XP, after you downloaded the file, right click on it and select copy. Go to Start > Run > type fonts and press enter. A new windows should open. Right click inside it and select Paste. Your font file should now be placed on the default location for this type of files and after a reboot, you will be able to use the font. For Windows 7 or Windows 8, things are simple. After you downloaded the font file, just open it, and click Install on the top of the page.