This video shows how to use TWRP 2.0 to flash CyanogenMod 7 on an Amazon Kindle Fire. In this case I'm updating an existing installation, but you'd follow the same steps to install a new custom ROM.
http://liliputing.com/2011/12/cm7-for...
This is the on-screen volume slider app that I forgot the name of during the video:
https://market.android.com/details?id...