How to light this type of basic, old fashioned gas-cylinder-powered gas oven?
Back when we had one of these, we used to turn on the gas, wait for a tiny while (I seem to remember 4-5 seconds), then drop a lit match into  the front center hole. That would light up the burners. I'd err on the side of too little gas until you're used to it, and it may take a few attempts 

Mom was pretty good at it, but that might have been through years of practice. 

This video goes through the whole process, though I could have sworn you didn't need to push down the knob