For all the equipment on the rv you should have a owner/operator manual. If you did not get any with the rv get the name of the manufacture, model number and serial number off of the item. Google the name of the manufacture and most have a site to download these manuals. You can also find many here on the forum, do a search for them. If no computer then remove the outside cover on the furnace first to determine if the heater uses a pilot light or has an electronic igniter. Turn on your gas bottle, the gas line will be empty so to get some gas in the line light one of the burners on your cook stove. After it lights, turn off. If the heater has a pilot light look at the base of the heater for a valve that has a off, on, pilot position. Some heaters have a valve with just a on/off position and a button you push to light the pilot. Rotate the valve to the pilot position or press the button and hold while you light the pilot with a flame. Continue holding the valve in the pilot position or button pressed in for aprox 30 seconds for the safety shut off sensor heats up and then release the button or return the valve to the on position. The pilot may not light instantly when you put the flame to it as you are still purging air out of the line. If the pilot continues to burn just turn the thermostat up and the heater should come on. If you have an electronic igniter turn the gas on, then on the thermostat turn the on/off switch on, if it has one. Turn the thermostat up and the heater should come on. If it has a on/off switch, this switch can be very hard to move to the on or off position. Hope this helps.
Jim L & Faye
2003 Silvarado diesel crew cab
2017 Silvarado, crew cab 1500 6.2L gas w/ 8 speed tranny