The procedure is provided in the manual under
SERVICE AND ADJUSTMENTS
and you can view the manual online at Manage My Home using this blue
link or the information in the
Sources link below
The fuel filter is attached to the end of the main fuel delivery line inside the fuel tank so you will need to drain the tank, preferably by running the unit until it is dry.
Then just remove the fuel cap/retainer assembly from the tank and lift it and the fuel delivery line out of tank until the filter comes out as well. Remove the old filter and install a new one on the fuel line and lower both back into the tank.