Change bootanimation of the Kindle Fire
That file is in the /system partition, which is mounted read-only, and even if you make it writable (which also requires you to be root), by default it's only writable by root. So it's not possible without rooting your device. The steps you have to take to be able to change your boot animation:


Root your device. The rooting method is device-specific, so I can't help you how; it's usually easy to find a  tutorial using Google.
Turn on root mode in ES File explorer (left side menu, root explorer).
Click on that menu item once more. It brings up a menu in which you can remount the /system partition in read/write mode.