Answer:
supposedly vampire do not exist but to become a psychic vampire, in theory, you would have to develop a need for the energies other humans possess, in which you would then have to hunt to obtain what you need and develop abilities that can assist you in obtaining what you need, it has to be both a physical and psychological need in order to obtain the abilities, it would require deep meditation and a deep understanding of what you are and what you want to be
by the way this is just my theory based on evolution and psychology