I figured it out. Using the username/password as part of the URL string (i.e. https://emily@socialcast.com:demo@demo.socialcast.com/api/messages/search.xml?q=e

I figured it out. Using the username/password as part of the URL string (i.e. https://emily@socialcast.com:demo@demo.socialcast.com/api/messages/search.xml?q=enterprise https://emily@socialcast.com:demo@demo.socialcast.com/api/me...) worked. I'm sure that there's a better way to do this, but this is just for fun anyways.