All visa applicants are advised to apply for their visa as soon as travel to the United States is contemplated, and not later than 3-4 months in advance.
Please confirm whether or not you need to apply for a visa. You may not need to apply for a new U.S. visa if you already hold a valid U.S. visa of the classification appropriate to your purpose of travel, or hold a passport eligible for travel under the Visa Waiver Program, or if you hold a Canadian passport.