Here is the lighting instructions in case you don't have a copy.
Depress and turn the control knob to the pilot position .
Depress the button and ignite the pilot flame while
keeping the knob fully depressed for a few seconds
Release the knob and check that the pilot flame stays lit.
If it goes out, repeat the ignition operation.
Main burner ignition
Depress and turn the control knob to the position corresponding to | symbol.
On release, the knob returns to the ON position.
Turn the temperature selection knob to the point corresponding to the desired temperature.
To close the main burner and keep the pilot flame on, depress and turn the control knob to the pilot position.
Turn the control knob to the OFF position.
Here a pdf. of it. SIT Gas Valve Manual