How do you add Ubuntu PPA repositories to Crunchbang 10?

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http://crunchbanglinux.org – I want to add the xorg-edgers ppa to my installation of Crunchbang so that I can get 3D acceleration on my laptop (which has an Intel 82852/855GM graphics adapter and is currently using software rasterization), but when I try running the command indicated in this thread http://ubuntuforums.org/showthread.php?t=1865295 all it says is "sudo: add-apt-repository: command not found". Help? (HowTos)