Open a terminal (it's the one that looks like a monitor on the task bar) switch to root (su root) type apt-get update when that has finished type apt-get install rcconf when done type rcconf in the terminal to launch the program use the arrow keys to navigate up and down and the space bar to select/deselect the options you want, tab to OK button and hit enter. Adding is alright but unless you know what a service does don't disable it as you could hose your box.