I am an international student in Korea, and I plan to travel to the United States and Canada for about 20 days in mid-August after graduation this summer. How do I apply for a visa to the United State

I am an international student in Korea, and I plan to travel to the United States and Canada for about 20 days in mid-August after graduation this summer. How do I apply for a visa to the United States and Canada? You are a China passport, so visas for all countries are separate, except that you already have a Korean visa, it is better to sign an American or Canadian passport. I think you'd better find a professional visa agency to give you a professional explanation so that you can prepare all kinds of materials conveniently. Or simply find an intermediary to help you get a visa, which will be more convenient.