Here's what you do. First open the side panel and look for the chimney and find a little panel at the base. Take out the screw and remove the cover.
You'll see the igniter and gas orifice.
your match and have the person inside push the RIGHT button and hold it down.
Outside hold a match over the orifice and light
the gas. Once lit have the person inside hold the button for 30 seconds.
When the button is released the flame should stay lit. Put the panel back and screw it on. Close up and all should be ok.
This is for MY heater. Yours will probably be different, but the same principals apply.