(Ubuntu 10.04 didn't install curl as default, you just need " sudo apt-get install curl " )
Step 2: edit /etc/apt/source.list , append the followed text to it, the point is replace the DIST with you Ubuntu release Codename, If you don't know that exactly, you can find it on the /etc/apt/source.list file, like me it is lucid , or launch the command "lsb_release -a" to get the Codename