Yes, the Twitter App registration can be a bit frustrating. It was much easier before they implemented their new(ish) security protocol. There was no registration required back then. But I suppose the plus side is that it is much harder for hooligans to hijack people's Twitter accounts. No worries though, I will do my best to get you fixed up.
The extension app is most likely already registered with Twitter. Try This:
1. In your browser go to http://dev.twitter.com/
2. At the top right of the page click "Sign In" and log in to your twitter dev account.
3. At the top right of the page click "Your Apps".
4. You will be taken to a page with a list of all of your registered apps. If your extension app is already registered, you should see it on the page.
5. Click your extension app name.
6a. You will now see a details page for your extension app.
6b. On this page you will see your apps consumer key, consumer secret and call back URL.
7a. You now have all of the information you need to proceed from step 7 & 8 of the Nice Tweets documentation http://trinitronic.com/index.php/Downlo ... ation.html
7b. Verify that you have properly transfered (copied & pasted) the consumer key, consumer secret and call back URL into your extensions settings at Joomla Administrator>>Nice Tweets>>Settings.
Let me know how it goes.
~ All the best