Could you provide some more information on what you mean by the "admin home page", and where you are getting stuck?

In general, the user experience goes something like this:

• Request an invite, accept it, register a Hub account
• Once logged in, you will be presented with a "lets get you started" page, with the action to register your Amazon account. If you don't have one, just follow the link to create one. Along the way, you can click "help" if you get stuck and need a little guidance. The whole process is actually quite simple.
• Once you have registered your Amazon account, you can then launch an appliance. Click on the launch link, select your appliance (optionally set advanced options), then launch.
• Your server will be launched and its information along with administrative actions will be displayed. You can then click on the IP address, webshell or webmin icons to connect to it.
• Optionally, you can SSH into the instance.

I hope the above helps, but the more information you can provide as to where you are getting stuck, the easier it will be to help.

It should be enough to just point the domain (DNS A record) to the IP address of the server running on EC2. If not, let me know, you might need to tweak the mediawiki settings, but I doubt it.

You might want to use an Elastic IP (translating Amazon's weird lingo, that means a static IP address that doesn't change). This would allow you keep the same DNS record, even if you terminate the server and launch a new one.

Regarding webmin (the web management interface), when clicking on the link it should open up in a new window/tab - didn't that happen? Do you have any suggestions that would make this clearer for other users?

I'm at a loss regarding the unregister/reregister, but I'm glad it's working for you now.