There are many creation myths out there and you will need to read them and decide which one you would like to use. For the West, there are three creations myths. The first one comes from the Greek and it can be read in Hesiod. He speaks about the origins of the gods and the successive ages of humanity. Human starts in the golden age and then digresses to the age where we are in.
The Romans also have a creation myth with a story of the flood as well. It is recorded in Ovid's Metamorphoses (book 1). We read of Deucalion and Pyrrha, who are like Adam and Eve. There were saved on account of their piety and through them, the world was repopulated.
The most famous story and some would not call it a myth, since it is foundational to Judaism and Christianity, is Genesis 1 and 2 in the Bible. But if you are going to write a paper on it, you should read up to Genesis 12.
Based on these three sources, you should be able to trace many themes, such as piety towards the gods, the decline of humanity, the role of pride and knowledge, and many more.