You can change your name on your account from the Members Area > My Account > Account Details page:
HipStamp: https://www.hipstamp.com/members/account/account-details
HipComic: https://www.hipcomic.com/members/account/account-details
HipPostcard: https://www.hippostcard.com/members/account/account-details
To update your name, change it in the "First Name" and "Last Name" fields, and then click on the "Save Settings" button.