I have been told Satan was originally the most beautiful and favored of all God's angels. Where in the Bible does it say that or reference to where Satan came from?
This is a very good question. You are correct, in that satan was considered the most beautiful of all the created Angels. The major reference to this is in the book of Ezekiel, where there is a lamentation over the King of Tyre. The references in these lamentations are believed to be a comparison to the state of Satan before His fall. Comparing the King’s power which was from satan. Below are the verses I am referring to in their entirety;
"Moreover the word of the LORD came to me, saying, Son of man, take up a lamentation for the king of Tyre, and say to him, 'Thus says the Lord GOD: You were the seal of perfection, Full of wisdom and perfect in beauty. You were in Eden, the garden of God; Every precious stone was your covering: The sardius, topaz, and diamond, Beryl, onyx, and jasper, Sapphire, turquoise, and emerald with gold. The workmanship of your timbrels and pipes was prepared for you on the day you were created. You were the anointed cherub who covers; I established you; You were on the holy mountain of God; You walked back and forth in the midst of fiery stones. You were perfect in your ways from the day you were created, Till iniquity was found in you." Ez. 28:12-15
At this point, the scriptures continue to give detail as to the fall of satan;
"By the abundance of your trading you became filled with violence within, And you sinned; therefore I cast you as a profane thing out of the mountain of God; and I destroyed you, O covering cherub, from the midst of the fiery stones. Your heart was lifted up because of your beauty; You corrupted your wisdom for the sake of your splendor; I cast you to the ground, I laid you before kings, that they might gaze at you. You defiled your sanctuaries by the multitude of your iniquities, by the iniquity of your trading; Therefore I brought fire from your midst; It devoured you, And I turned you to ashes upon the earth In the sight of all who saw you. All who knew you among the peoples are astonished at you; You have become a horror, And shall be no more forever." Ez. 28:16-19
You also mentioned that satan and his angels were cast out of Heaven. This is true and the account of that is given in the book of Revelation where is records that satan and one third of the Angels were cast out. The reference to the 'dragon' in these verses of Revelation is satan and the 'stars' here are angels;
"And another sign appeared in heaven: behold, a great, fiery red dragon having seven heads and ten horns, and even diadems on his heads. His tail drew a third of the stars of heaven and threw them to the earth. And the dragon stood before the woman who was ready to give birth, to devour her Child as soon as it was born. She bore a male Child who was to rule all nations with a rod of iron. And her Child was caught up to God and His throne. Then the woman fled into the wilderness, where she has a place prepared by God, that they should feed her there one thousand two hundred and sixty days. And war broke out in heaven: Michael and his angels fought with the dragon; and the dragon and his angels fought, but they did not prevail, nor was a place found for them in heaven any longer. So the great dragon was cast out, that serpent of old, called the Devil and Satan, who deceives the whole world; he was cast to the earth, and his angels were cast out with him." Rev. 12:3-9