the fuel filter is just infront the rear nearside wheel (passengers side)
you will need pair of clamps to clamp the fuel lines eitherside of the filter then squeeze the tabs on the
fuel line that connects onto the filter & pull each end off then unto the clamp that holds to filter to the body of the car & slide out
then fit the new filter put on the pipes & make sure they are secure then remove clamps then start engine
you will find it will take a little time to start due to the filter having to fill up so just keep cranking until if fires up.
piccy of what it looks like here m8. the fiestas are the same as the ka.