Sadly, only fragments survive. Epicurus had little patience with religion, which he considered a form of ignorance. He was particularly eager to help people loose their fear of the gods. He did, however, also say that the gods existed, although they lived far away in space somewhere and had little or nothing to do with people on earth. Epicurus felt that it was useless to argue over metaphysics, that there was no such thing as a soul that lived after death, that we arrived at our present condition by means of evolution, and that we had the quality of free will.
All knowledge comes from the senses.
Virtue for Epicurus was a means to an end. That end is happiness. It is good to feel pleasure and to avoid pain, but one needs to apply reason to life. Sometimes pain is necessary in order to gain happiness. Other times, pleasure leads to more suffering than it is worth.