Note: the admin pages have been redesigned since the screenshots in this documentation, though the functionality is essentialy the same. The documentation will be updated to match.... soon.
To set an A Record on a domain registered with GoDaddy, follow their Adding or Editing A Records instructions.
In step 4, use the IP Address 83.136.248.56
Note that changes to your DNS settings can take up to 24 hours to propagate through the Internet.