When you create an account, you will notice that everywhere that you see your name or login, a small image called an avatar is displayed alongside it. These images are automatically generated and managed via a third party service called Gravatar.
By default, you will be given a default avatar. To create your own avatar with Gravatar, just head on over to their site at http://gravatar.com and create an account. The service free, and very easy to use.
Make sure that you register with the same email address that you used to register with Codaset, as Gravatar relies on that email. Once you have registered for a free account with Gravatar, you will be able to upload your own avatar to their site. Shortly after that is completed, you will notice your avatar on Codaset.com start to update to reflect the change your made.
And that's it! Easy peasy!