On the species fact sheet you can read a brief cultivation description: http://www.nzpcn.org.nz/flora_details.aspx?ID=964
Also according to Metcalf (1987). The Cultivation of New Zealand Trees and Shrubs. Reed Methuen: Auckland (p. 194).
"It should be given a good, rather rich well-drained soil, and while it prefers a moist situation it will also grow in rather dry places.It is easily damaged by heavy frosts, particularly when young, and when grown in frosty districts should be grown in a sheltered position."
He states that kawakawa makes a good tub plant as long as it is well fed, and will readily withstand pruning to keep it shapely.
Good luck!