To travel to the U.S. under the Visa Waiver Program, you need to obtain an electronic travel authorization called an ESTA (Electronic System for Travel Authorization).
You can apply online through the official U.S. government website:
https://www.cbp.gov/travel/international-visitors/esta
You will need to complete a form, provide your personal and passport information, and pay the fee by credit card.
We recommend applying at least 72 hours before your departure. Once approved, the ESTA is usually valid for two years (or until your passport expires).