Just google “how US Elections work” and you will find sites. I found this description. 
Presidential Elections
The President of the United States is elected by the Electoral College and not directly by the population. Each state is assigned electoral votes based on the number of senators and representatives that state has in Congress. Each state has two Senators. The number of representatives is determined by the states population but is never less then 1. Thus small states with a small population are overly represented in the Electoral College. One candidate wins all of the electoral votes in all states except Maine and Nebreska. Their two electors are chosen by statewide popular vote and a single elector is chosen in each Congressional district.