RE: new to 4 strokes.
The fuel tank is set up the same way as it is for the a 2-stroke engine. One line is the fuel pickup (the one with the clunk on it), one line is the vent line (from the muffler), and the 3rd line is optional. If you use a third line it will normally be used a fill line going to something such as a fuel dot.
Hope this helps
Ken