The "how" of changing the fuel filters should be self-evident, by disassembling them from the car, and replacing them with suitable new filters.

What you need to do is either use the hand pump in-line to refill the fuel filters and fuel line, by cracking the outflow bolt downline from the secondary filter, until fresh fuel spurts out before closing, or, back filling the secondary fuel filter, then flooring the foot feed when cranking.

I prefer the in-line fuel hand pump to the floorboarding method.

Also, change when the engine has been running already, to ensure a quick start up.

Personally, I backfill the secondary fuel filter with Powerservice, when I have it on hand, over either ATF or diesel fuel.