By main points, I'm assuming you are asking about major themes that are present in the pamphlet. There are several of these, the first one being Machiavelli's purpose for writing The Prince in the first place. In his dedication to Lorenzo De'Medici, Machiavelli states his purpose for writing the pamphlet is to illustrate the role that Fortune plays in the success of a Prince. He is seeking the favor of Lorenzo De'Medici and adds that although he cannot offer gifts such as gold, rich cloth, or music, he can offer his "knowledge of the actions of great men" and the ways in which they attained and kept power.
Each chapter of The Prince discusses a different major topic on ways to acquire and maintain power. Machiavelli discusses the two types of Princedoms, hereditary and new Princedoms, how Princedoms are acquired either through the Prince's own arms and merit or with the help of others and good Fortune, and how Princedoms can be attained through committing crimes. So, you could say that one of the major themes is how to acquire a Princedom.
Another major theme that is seen throughout The Prince is the question of whether it is better to be feared or loved as a ruler. It is a topic that has been debated ever since Machiavelli first presented the idea. According to Machiavelli, a Prince should strive to be "accounted merciful and not cruel." Although he makes this statement, his list of examples that follow this quote show that those rulers who have a reputation of being cruel are more successful than those who have a reputation of being merciful. This dichotomy present in the text is one that creates debate.
Machiavelli spends much of The Prince also discussing the different types of troops that can be used to acquire and maintain a kingdom. This could also be considered a major theme. He discusses the difference between using one's own arms, or hiring mercenaries and the benefits and costs of using each.
Of all of the major themes though, the one discussed the most throughout The Prince is the role of Fortune. Of all of the actions that a Prince makes, none of them can be successful without good Fortune, and Machiavelli explores this idea at length. He argues the case that "Fortune is the mistress of one half of our actions." It is important to note that the word "Fortune" is always capitalized throughout The Prince and that it is often referred to as a person rather than as an abstract idea.
In short, you could say that there are four major topics discussed: the role of Fortune, the different types of Princedoms and how they are acquired, whether it is better to be feared or loved, and the different types of military units and how they should be utilized.