To be able to install most software to your own install of BackTrack that does not come from the repo's you will need to prepare the kernel sources.
This is very simple to do and will only take you a couple of minutes.
At the terminal, issue the following commands:
Please remember to copy and paste these commands into your terminal prompt as formatting can make long lines wrap over into two or more lines !
apt-get install linux-source
cp -rf include/generated/* include/linux/
And that's it.
Other than resolving any dependency requirements of the software you wish to install, you are good to go.