Joomla website alteration

Please look at the full members directory and associate members directory on the website [login to view URL] How do we make these members list alphabetically? We need for website readers to find people easily when we get a long list. The surnames should be listed alphabetically. I wondered if we should have had a separate field for first name and second name in our registration forms which can be found in the "sign up" pages. Is this something you can fix for us.