It isn't there!
Most of Isaiah 14 is a long rant against an egomaniacal, tyrranical king of Babylon. This is clearly seen in context:
Isaiah 14: 3 On the day the LORD gives you relief from suffering and turmoil and cruel bondage, 4 you will take up this taunt against the king of Babylon: How the oppressor has come to an end! How his fury has ended!
Isaiah is clearly talking of a man here. And again:
Isaiah 14: 12 How you have fallen from heaven, O morning star [Lucifer in some translations], son of the dawn! You have been cast down to the earth, you who once laid low the nations! 13 You said in your heart, "I will ascend to heaven; I will raise my throne above the stars of God; I will sit enthroned on the mount of assembly, on the utmost heights of the sacred mountain. 14 I will ascend above the tops of the clouds; I will make myself like the Most High." 15 But you are brought down to the grave, to the depths of the pit. 16 Those who see you stare at you, they ponder your fate: "Is this the man who shook the earth and made kingdoms tremble, ...
It was later that the Jews and early Christians began to conflate the snake in Genesis, Satan in Job and Lucifer in Isaiah into a single personage named Satan. I suspect that this was accomplished under the strong influence of Zoroastrian belief to which the Jews were exposed during the Exile.
The reality is that Lucifer is the ironic name for a Babylonian king, Satan is an angel in God's service and doing God's will and the snake is, well, just a "garden variety" talking snake.
In the Latin language Lucifer means bright morning star, a reference to the planet Venus. In Isaiah it is used ironically and tauntingly in reference to a Babylonian king. In the Latin Vulgate version of the Bible Lucifer is used twice in Revelation in reference to Jesus in the sense of light coming into the world. Lucifer is not Satan.