intstall firefox on kali linux

#apt-get remove iceweasel
#echo -e "\ndeb http://downloads.sourceforge.net/project/ubuntuzilla/mozilla/apt all main" | tee -a /etc/apt/sources.list > /dev/null
#apt-key adv --recv-keys --keyserver keyserver.ubuntu.com C1289A29
#apt-get update
#apt-get install firefox-mozilla-build

Unzip .tar.bz2

tar xvjf filename.tar.bz2
Which will untar it to the current directory. Normally (99% of the time) it will create it's own subdirectory so you don't need to worry about that.
Just so you know:
tar - Tape ARchiver
And the options:
x - extract
v - verbose output (lists all files as they are extracted)
j - deal with bzipped file
f - read from a file, rather than a tape device

"tar --help" will give you more options and info