This is a really neat fuelling system that suits most models where a remote fuelling point is needed. This is very popular with scale modellers as it can be mounted in out of sight places.
Install the flush fuelling flanges to either side of your fuselage wall.
Make sure you have enough fuel tube to reach from your tank to outside your fuselage via the fuelling flange
Run the fuel pipe from your filler pipe on your tank and through the fuel filler flange on your fuselage
Insert the stopper into the fuel pipe and push firmly into the filler flange.
Now for the easy part. Pull out the fuel stopper and remove from the fuel pipe. Fuel your model in the normal way and replace the stopper then push back into the flange. How easy is that!