There are a couple of different things.
1. You'll need to upload any web-accessible files to the www directory (or a subdirectory of it) in order for them to be accessible from the web.
2. It appears you just updated the name servers on the domain today, so you may need to allow some more time for propagation to complete before using the domain name (during this time, you can use the temporary access information contained in the Activation Letter). Propagation normally takes 24 hours to complete.
If you should need further details, please email us at the Service Desk:
and we can provide more specific information.
Hope this helps,