$V=-PE cos \theta$$V=-PE \cos \theta$. From this expression, we can deduce that the potential energy is dependent on the angle of orientation, which varies between $-pE$ when the dipole is aligned with the field and $pE$ when the dipole is aligned against the field. Because the energy is least when the field and the dipole are parallel to each other, it follows that this is the most favored orientation. i.e. the dipole tends to align itself with the field.