How do I use Vokera Excell 80SP?!!?

just moved into a flat and no idea what the symbols are or how to set it up...do I leave the left handmost of the three knobs on "O" or should it be on the other 2 symbols (and what do they mean, one I guess is heating, and the other is h/water - but not sure which).
This is all way over my head - not had to deal with these boilers - need an address for a how-to-use booklet!