How does my boiler work, i have no manual. anyone have any ideas?

i have a Glow-Worm Flexicom 30cx gas boiler in my kitchen, and ive turned it on, and i have this little pad on the wall, and to set the heating it has programms, either, on continiously, or once- which is on at first on, off at last off, automatic, or off, i dont know which one to put it on so it doesnt use to much gas, i want it so if i turn the dial down by the wall the boiler will go off, but if i turn the dial up on the wall, the boiler will automatically go on? which setting do i put it on?