Queen Hecuba was pregnant and had a dream of her child being a flaming torch. This was later interpreted to mean the child would be the downfall of Troy and had to be killed.
Agelaus was called to kill the baby. When he got to the mountain he found he could not kill this child so Agelaus just left Paris there. But a bear came and took care of him so this was seen as a sign that Paris should be kept alive.
One thing Paris did when he was older was he challenged his prized bull against others. Ares accepted this challenge and one. But Paris proved himself still and Paris showed the Gods he was trustworthy.
Zeus was throwing a wedding in which Eris wasn't invited because she causes to much chaos. She found out about this and threw an apple in the crowed of people that said "for the fairest."
Many goddesses fought over the apple but it came down to three Aphrodite, Hera, and Athena. Zeus had to choose one but couldn't and sent Paris off to a mountain to choose where the Goddesses would try and bribe Paris.
Aphrodite says she will give Paris the gift of love through the beautiful woman Helen. Paris gave her the apple then stole Helen from her household. The husband of Helen vowed to take her back and destroy the land of troy, this would start the trojan war.