I have no idea how to use this thing. Got it for Christmas. Would like to use it with my Kindlefire amazon music. How do I install for use?

From here or your main Amazon Online Account. Delete all payment methods, log out and then back in again. Re-enter the new card details.

Change Your Amazon Music Unlimited Subscription ...

Amazon.ca https://www.amazon.ca > help > customer > display
Go to Your Amazon Music Settings to change your payment method. Amazon Music forum.

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  Update Your Payment Method - Amazon Customer Service

  https://www.amazon.ca > help > customer > display
  Click Digital Payment Settings, under Edit Payment Method. Select a different payment method from the list or add a new one and click Continue. Important ...
  
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Use Amazon apps!

Did you turn the Kindle Fire on immediately after inserting the charger?
The battery may be so low that it will not operate until after it has charged for more than 24 hours.
If that is the case, it is also possible that the battery life has been permanently compromised and won't last long even if you finally get it to work.

It is also possible that the charging port on the bottom edge of the Kindle Fire has been damaged...possibly from forcibly inserting a charging cable upside down. If the port is damaged, the cable would not make contact properly and would not charge.

Follow instructions here: http://www.amazon.com/gp/help/customer/display.html?nodeId=201539930

Visit Amazon, choose a book or books and download to your Kindle and then read books.

I have the same model and had not had that issue. None of the buttons work (hold each down for 10 seconds)

Hello, is anyone there? How do I change the country setting on my kindlefire hdx?

Have you tried using a different power cord. We have gone through 2. Grandkids.....!

See

http://kindle.s3.amazonaws.com/KindleFireQuickStartGuide.pdf

then

http://kindle-fire-updates.s3.amazonaws.com/Kindle_Fire_User_Guide.pdf