The registration process is actually very easy.
The first step is to download and install There. You can download the client installer by going to http://www.there.com/downloads in an Internet Explorer window.
Once it is downloaded, you can doubleclick and run 'Install_There.exe' to run the installer. After it completes, you will automatically be taken into the registration process if you click the 'Continue' button.
If you already have the client software installed, and just need to create an avatar, please visit this web page in an Internet Explorer window:
http://webapps.prod.there.com/register
It will take you through the avatar creation process.