I haven't read Homer, so I am not sure about the story.
But i have looked it up on wikipedia. According to wikipedia, Helen was the most beautiful woman in the world, and of her powerful Greek suitors, she chose Menelaus. Her father made all suitors promise to defend the marriage that she chose.
Zeus held a banguet for all the Gods and Goddesses, but didn't invite the Goddess of strife, because he didn't want any trouble. She was angry and threw a golden apple into the midst of the banquet with "Kallisti" written on it (which means "for the most beautiful"). The three most beautiful goddesses, Hera, Athena and Aphrodite argued over who should claim the apple. They asked Zeus to choose. He didn't want to choose, because it would upset the other two, so he said that Paris should choose. So the goddesses found Paris and bribed him to choose them. They offered him all different things, and Aphrodite offered him the love of the most beautiful woman in the world.
She was Helen, and she was married. He went to Greece and Aphrodite carried out her promise by getting Eros to shoot Helen with an arrow, so that she fell in love with Paris, and they eloped.
Her father then called on the suitors to honour their oath, and the Trojan war started.
It all then gets more complicated, and I will have to find time to read the lot, but first I have to read my council tax bill.