Possibly the easiest way to do it is to get an Elastic IP from Amazon. An Elastic IP is essentially a static IP that you can attach to an instance so it doesn't change. You then use your domain providers DNS tools to point your IP to your Elastic IP.

Note that one Elastic IP per instance is free, but only while the appliance is running. If the Elastic IP is not attached to a runnign instance then you are charged an hourly rate (IIRC it's $0.005/hr ie. 1c per 2 hours). Check AWS pricing to be sure.

The other option is to set the Hub up to handle your domain name. Then you can use HubDNS to update the IP address. That works quite well for running instances, but can be really slow to update when the IP changes. Generally it takes about 5-10 minutes for the update to complete. We have plans to try to improve the performance of HubDNS but we're not sure when that will happen.