I don't have the model number do to the sticker being worn. How can I get an instruction/service manual?

Look at gas valve and turn knob to "pilot" then either you will have a (Usually red) button to press or you will press in on knob to let gas flow to pilot light. After purging air from line it should light whereupon you will keep button or knob pressed in for a minute or so to get thermocouple hot enough to keep flame lit. After flame stays lit turn knob on gas valve to next step and you are done. If flame will not stay lit you may need to adjust it or replace thermocouple.