The Kindle Fire original keyboard is so small that it's not easy to use.Read this articlr and you'll learn how to replace the original keyboard. Rooting is needed.

1. How to change Kindle Fire
keyboard
www.epubor.com

2. How to change Kindle Fire keyboard
The Kindle Fire’s original keyboard always get me crazy.
It’s so small that it’s easy to type the wrong words. You
may want to install another keyboard app to replace the
original one – just like what you do on an Android device.
But Kindle Fire has no any options for you to change the
input method as Amazon has block this feature.
But if your Kindle Fire is rooted, then thing would get
easy. This article will tell you how to change Keyboard on
a rooted Kindle Fire

3. 1. Root Kindle Fire and allow installation of applications
The first thing you need to do is to
root your Kindle Fire. You can refer
to some tutorials:
• How to root Kindle Fire
• Rooting Kindle Fire with one click
And you also need to allow Kindle
Fire to install third party apps. Go to “Settings” – “Device” and
enable “Allow Installation of Applications”

4. 2. Install keyboard app
Visit download.pandaapp.com to get and install keyboard app on
your Kindle Fire. Here I choose the ICS keyboard, the Android 4.0
original keyboard

5. 3. Move keyboard app to system directory
Open ES File Explorer(you can
get from Kindle App store) and
go to /data/app. Find the ICS
keyboard app you just installed
and paste it at /system/app. The
app name may have changed.
You can find it by app icon.

6. 4. Reboot device and install keyboard again
Reboot your Kindle Fire and go to /system/app again by ES File
Explorer. Tap the ICS keyboard and you will be asked whether to
replace the app. Choose “OK” and install.

7. 4. Reboot device and install keyboard again
Tap anywhere you can type
words and a window will pop
up to let you choose the input
method. You can see the ICS
keyboard in the list. Choose it
and you can see the original
keyboard has changed into ICS
keyboard.

8. 5. A tiny bug you may meet
This trick is simple but it’s
not perfect. A tiny bug has
been found that the next
time you reboot Kindle
Fire, the keyboard app
may crash. This situation
only happens on some keyboard apps, not all of them. If you
meet this, just go to /system/app and reinstall the keyboard
app then the warning window will disappear and it won’t pop
up any more
Source: http://www.epubor.com/how-to-change-kindle-fire-keyboard.html