Realistically, it is not really Hawaiian since the laws forbid transporting the plant material across state lines but the seeds maybe originally from a Hawaiian plant, currently grown in California.
The short answer is you don’t, and it probably isn’t.
The long answer: The strains that were bred and developed on the islands of Hawaii are extremely unique and closely guarded by the people of the islands. The Hawaiian genetics that do make it stateside, are often only weak imitations of the famed Hawaiian strains. Recently several prominent breeders have begun bringing true Hawaiian genetics to the marketplace and growers, worldwide, are starting to cultivate these precious varieties.
The strains Hawaii is known for are Narrow Leaf Sativa varieties, because the Broad Leaf Indica varieties tend to suffer from too much mold damage to produce a viable crop. These narrow leaf strains are rare in California because they do not produce viable flowers until December or even early January. This longer finishing time also effects indoor cultivation, and as a result, commercial growers rarely cultivate the long flowering sativa varieties. On top of a longer cultivation cycle, sativas are often hindered by a less desirable appearance than today’s flashy hybrid varieties, so all those seeking Hawaiian strains should try not to "judge a book by its cover".
As one would expect, Narrow Leaf varieties have become extremely rare and they do not often make it to dispensary shelves these days. With market demand, and willingness to compensate farmers for the difficulties of marketing these varieties, sativas will start to make a come back. Just keep asking for them at your local dispensary and help educate other patients about the wonders of these endangered cannabis genetics.
Pua Mana `Ohana is a Hawaiian Seedbank that is starting to release their genetics. Some dispensaries carry their seeds in California, Oregon and probably elsewhere. Their strains can be found on Seedfinder and Leafly.