I did mine simply by contacting through the website.
My WorldPerks account had my full first name, middle initial, and last name. When they merged it with my SkyMiles account, for some reason (probably what was on the SM account), they gave preference to the name from the SkyMiles account which was Matt rather than Matthew, no middle initial, and my last name. A simple Contact Us message resolved it, though it took I think a week or so.