configuring hostname on Amazon EC2 Ubuntu AMI

Hi,

I installed ejabberd on Amazon EC2 Ubuntu AMI following
http://blog.kenweiner.com/2008/05/ejabberd-on-amazon-ec2-ubuntu-ami.html
installation was ok but now I'm stuck in the step about configuring the hostname in the ejabberd.cfg file

%% Hostname
{hosts, ["????????"]}.

I want to be able to access the admin site from outside the EC2 server but I have no idea what do I need to configure to achieve this. Has anyone experience doing this?
Do I need to modify something in the Amazon console?

Thank you!!