Introduce plants that butterflies can feed on. Plant flowers that are native in your area, especially those in red, yellow, orange, pink, or purple. Plant the flowers in full sun during the day, when butterflies feed. Try to coordinate flowering plants so that one of them blooms all the time, so the butterflies always have food. I would try to avoid using any insecticides, they can kill insects your are trying to attract. Provide a shallow pan of some sort with coarse sand in it, for an area where the butterflies can congregate. Butterflies like to nibble on peelings, cores and slices of fruit. I would attract butterflies in your area, rather than releasing store bought exotic species. They more than likely would die off in the unfamiliar environment.