Applying for an immigrant visa to the United States tends to be more complicated than applying for a non-immigrant visa. The process starts with a family member or employer in the United States filing a petition to bring you to North America. This petition is filed with the USCIS, which will either approve or deny the petition.
After the petition is approved, you can begin filling out Form DS-260 online. Visit the website of the US embassy in your country to get started.