The instructions apply to all Amazon Fire tablet models.
How Do I Change the Keyboard on My Fire Tablet?
Go to the Amazon Appstore on your gear and download a third-party keyboard app.

A search for keyboard will return dozens of free apps.
You might want to grab a few so that you could try out different ones.
You caninstall Google Play on your Fire tabletto see even more app options.

Open theSettingsapp on your Fire tablet.
Scroll down and tapDevice options.
Scroll down to theThird-Party Keyboardsection and tap each of the keyboard apps you downloaded to enable them.

Go back to the Keyboard & Language screen and tapCurrent Keyboard.
Choose your preferred default keyboard.
When you return to the previous screen, tapCurrent Keyboardagain, then tapKeyboard options.

The configs you see will depend on which keyboard app you’re using.
Some will direct you to the machine’s default keyboard configs while others offer advanced customization options.
The keyboard includes a dock so you could use it as if it were a laptop.
Not all Fire tablets are compatible with Bluetooth keyboards.
When shopping for keyboards, check to see which tablets the keyboard supports.
FAQ
First, put your keyboard into pairing mode according to the manufacturer’s instructions.
Then, turn on Bluetooth on your tablet: Go toSettings>Wireless>Bluetoothand activate the feature.
Finally, choosePair a Bluetooth Deviceand select your keyboard when it appears.
A wired keyboard must have a USB-C cable (or an adapter) to connect to a Fire tablet.
Just verify that any keyboard you get is compatible with the Amazon Fire.