Presuming that you are getting gas to the top burners, thus you don't have a problem with supply, at least not to the stove overall.
As for lighting, turn the knob to "Pilot" and push the knob in and hold your lighter at the pilot orifice while continuing to hold the knob in. Do not turn it to any temperature. If you've not got a pilot burning, a temp setting will do nothing.
Wait until you get a flame at the pilot and continue to hold the knob in for a while. There is what is called a thermocouple there that the flame from the pilot envelopes while burning. The thermocouple must heat up to a certain temperature in order to keep the gas flow to the pilot going. If it isn't heated up enough, the pilot will go back out when the knob is released.
Once the pilot has heated the thermocouple for a while, let the knob back out. If the pilot stays lit, then you can turn the oven control to a temperature of your choice.
A thermocouple is actually a safety device that will cause the gas flow to the oven to stop, should the pilot light go out for any reason. So, it it is an older stove, that thermocouple may need to be replaced. If it isn't old, the above steps should help.
Over on the RV Dreams website, Howard posted a daily journal entry where he was making different repairs to their Cambridge fifth wheel. In it, he includes images of the pilot light and thermocouple. You might check this link out.
http://www.rv-dreams-journal.com/201...gfield-la.html
Terry