Use a comma to separate the elements in a sentence (3 or more things), including the last two. "He hit the ball, dropped the bat, and ran to first base."

This is actually quite a difficult question. I would say that commas are used when listing items, when seperating clauses in a sentence, and when indicating what would be a pause in spoken speach. However, when listing items, it is usually correct to use the conjunctive "and" before the last noun or item listed. For example, "I went to the store and bought apples, pears, pineapples, grapes, watermelon, and oranges". Your question is phrased wrong; it should be: "How do I use commas in English?", or, "How is the comma used in English?", or you could say, "How does one use the comma in English?".

I think this link may help http://www.ego4u.com/en/cram-up/writing/comma

Não sei que você encontrou quais problemas com a commas. Mas senti fácil usar ele quando eu aprender inglês, como não tem muita diferença entre chinês e inglês. Acho é melhor que você mostre seu exemplos.

Ok, thanks!