How do I become an American citizen?

This would depend on a whole lot of factors, the easiest way however may be through sponsorship by a family member who is a citizen

There are various ways to gain U.S. citizenship, each with different determining factors. However, the easiest way still remains sponsorship by a family member who is already a U.S. citizen

Several ways... through birth, naturalization, or acquiring citizenship from U.S. citizen parents.