You should start applying for an F-1 Visa application 120 days before the start of your course.
An F-1 Visa is valid for up to 5 years.
You can enter the US 30 days before the start of your studies under an F-1 Visa.
You can also stay for maximum of 60 days after graduation under an F-1 Visa.
Click here to know more about an F-1 Visa