Start at Dawn Winery, which is southwest of Mondstadt, take the path south, all the way along the coast, and you will come to an area called Stone Gate. The stone Gate will send you down some stairs to the corridors of a mountain, always continue south until you reach the statue of the seven in Dihua Marsh. Talk to the statue to reveal the surrounding area, and there you can see the Wanghu Inn. Go that way and continue south, past Guili Plains, until you reach the Statue of Seven, north of Liyue Harbor.
Follow that same path, and you will finally arrive at the port of Liyue which becomes visible once you interact with the Statue of the Seven.
I hope that with this guide you can easily reach the port of Liyue and know how to find the port of Liyue Genshin Impact.