If you've set your mind to study a Master's degree at a university in United States, then you must prepare and avail all the materials and documents to show prove that your are the best fit or you fit for admission in their universities application requirements. First you need to use these documents to provide and complete personal information, previous qualifications, financial information, and a personal statement.
To apply to a university in the USA, here are the documents that you will be asked as a preliminary:
1. your passport or national identity card;
2. transcripts or records of grades (high school and/or university);
3. copies of past diplomas or certificates;
5. motivation letter or statement of purpose;
6. reference letters from past employers or teachers;
7. writing sample.
Because you'll study an international degree in English, you'll have to present a language certificate. Most U.S. universities will accept one of these language tests: IELTS, TOEFL, C1 Advanced. If you don't meet the minimum language requirements, you will have to improve your skills and scores by taking an English preparation course.
Depending on the subject or specialization of your chosen Master's, you might also be asked to provide scores for additional tests including: GRE, GMAT, LSAT, MCAT, ACT, SAT. Depending on your degree subject, you might also be asked for writing sample, portfolio, or list of patents.