Using a domain name for a website

I know this should be a pretty easy thing to do, but I'm having trouble.

Say I bought a domain name from 123-reg.co.uk "example12345.com". And I have a website hosted on AWS called something like http://ift.tt/2uhr9lL.

I have read the following blog: http://ift.tt/2tjHmJK and followed the steps, but still have 2 issues/questions:

1) I have configured "web forwarding" on 123-reg.com to forward requests to example.com to my convoluted AWS address, but when I type in example12345.com to a browser, it just says the DNS can't find that domain name. I set this up weeks ago, and did manage to see it work a couple of times, but weeks later it doesn't work anymore.

2) On the occasions I did see the web forwarding working, I notice that the browser displays the convoluted AWS address after the redirect happens. Is there a way to configure it so that users type in example12345.com into the browser, and then it's that address that is always displayed in the browser address bar whilst they are browsing around my website? Surely I need more than just web forwarding and a redirect?

Thanks!