I sent an email with zip file containing .apk files attached. You will need to use a PC to save the attachment to a known location, then unzip the files to a known location so you can find them to install on the Kindle Fire.
You need to install the Easy Installer app from the Amazon Market on your Kindle Fire. Enable sideloading on the Kindle Fire by pressing the round star shaped icon near the battery icon to select settings then select More then seledect Device then find Allow Installation of Applications From Unknown Devices and select ON.
Now you will need a micro USB cable to plug the Kindle Fire into the PC. Use a file browser on your PC to copy the .apk files onto the root directory of the Kindle Fire. Unplug the Kindle Fire from the PC.
Launch the Easy Installer app on the Kindle Fire. You should see a list of files that you copied to the Kindle Fire. Select the ones you would like to install by checking them off, press install.
Press the home icon on the Kindle Fire, the select Apps from the top menu. You should see your new apps on the bookshelf.
Posted with my HTC Thunderbolt.