how to get heat to work on necht oven?

I have just had a necht oven installed and would like to know if anyone can tell me how to getthe heat to work. Dont know which model it is, but it has got three knobs at front - left hand one for temp., middle one for timer, and right hand one for which part of oven to heat. I turned the temp. up to the temp. iwanted,and then turned the right hand knob to the part of the oven I wanted to heat, but no heat, just the fan worked. Could someone help me - I'm hoping it'sjust something simple that I havemissed, as I haven't got an instruction manual.