After you have the web server setup and running locally you have to expose it to the wider world (the internet).
Depending on your setup I would expect you to have a router that talks to your ISP. You need the IP address of your router http://www.whatismyip.com/ and setup GoDaddy with that IP address against your domain name.
There is then the small problem that your ISP may issue you a new IP address in the future. Most ISP have the option of a static IP address if you ask nicely.
Then you need to setup port forwarding on your router so that when traffic from the internet hits it it knows to send http(port 80) traffic to your Pi.