In order to apply for admission to a university, you should write to the department that you are interested in and ask for application forms and information about their program. In order to be admitted to an American university, you have to prove that you have enough money to go to the United States and live there for one year. The amount required is based on the tuition of the institution where you are applying and the cost of living in the area where it is located. A student visa requires foreign students to enroll full time and take a certain number of credits each term, except for the summer term. It is a good idea for foreign students to start from the summer term, because that allows, then to take only one course and adjust to academic life gradually.
Many schools have language institutes where foreign students study English.
Admission to the language institute is not the same as admission to the university. You have to apply to the university while you are studying English at the language institute. Usually credits you earn there do not count toward a degree. In some cases, you may be admitted to a university but still be required to improve your English proficiency in English language courses. This is a better situation, since you can take both regular course and English language courses.