This part is fairly simple. If you are using AWS, your server does not get a public IP by default. This means that from the internet, your server is only accessible by that public DNS name when it is first launched.
However, it's fairly straightforward to give it a public IP using Amazon's Elastic IP service.
- From the EC2 Navigation, select Elastic IP on the left-hand side
- In the main section, select Allocate New Address
- Make sure EC2 is selected, and cick Yes, Allocate
- Right-click on the newly given IP address and select Associate.
- Choose your newly created instance and then Yes, Allocate
Congratulations! You have successfully allocated a public IP address for your AWS Instance. In order to get your domain name to point to it correctly, log in to your DNS host and create a DNS A Record for [yourserver].com to point to that IP address. How this is done exactly will depend on your DNS host.