Just hover over the "profile" tab, then choose "account settings." On that page, scroll down to the question about "what type of member are you," and you'll see a dropdown box. Click on the arrow, and it'll give you the various options, including something like "adult with XLH/parent of patient." Once you've chosen the option, scroll down and click the "save changes" button.
If for some reason it doesn't work, PM me and I can change it as an administrator.