If you don't get an answer, maybe the information in one of these other threads will help:

• http://www.amazon.com/forum/kindle?_encoding=UTF8&cdForum=Fx1D7SY3BVSESG&cdThread=Tx16A9K5JFE35AT
• https://support.mozilla.org/en-US/questions/935734 When will Firefox Mobile for Kindle Fire be available in Amazon App store and why has it not been available sooner?
• https://support.mozilla.org/en-US/questions/930780 Why not Kindle Fire?

The only thing available right now is an app called Firefox sync

And this app is pointless it does not function as a browser just a sync for your browser history and bookmarks from your pc.

See this post from the Amazon Kindle forum thread I linked earlier:
Quote:

Posted on Apr 2, 2013 9:10:43 AM PDT
Last edited by the author on Apr 2, 2013 9:24:28 AM PDT
Colin Hildinger says:
D. Hyde: It's possible that Amazon has fixed the issue, as it was really a problem with their ICS package, and they just updated things. I'll test an old version just for grins.

That said, version 20 is now in the release channel, so the fix for the Kindle Fire HD is now in stable release anyway:

https://ftp.mozilla.org/pub/mozilla.org/mobile/releases/latest/android/en-US/

Edit:

Confirmed with release 19 -- Amazon fixed the Kindle Fire HD software a few days before the Firefox workaround made it into the stable release. Go figure. 

According to the 2/18/13 post by kbrosnan in this thread and the related bug 791419, Firefox 20 for Android should work on the Kindle Fire HD.

As far as downloading the Firefox APK file from the FTP site, see also https://wiki.mozilla.org/Mobile/Platforms/Android#Download_Firefox_for_Android

P.S. Here is what kbrosnan wrote in his 2/18/13 post in the thread I linked , in case it helps:

The Kindle Fire HD crash is only fixed in Firefox 20. I recommend Firefox Aurora for non-store installs as it includes an updater. http://www.mozilla.org/en-US/mobile/aurora/

We don't have any plans to ship Firefox in the Amazon app store because they modify our software. 

The mobile/aurora link gives detailed installation instructions.

solved