Welcome back to Understanding OAuth - Tweeting from Scratch. This is Part 2 of the two-part series and picks up right where we left off in Part 1 with your returned Access Credentials. Since obtaining the credentials is the grueling part of the process, there's not much more left to do except posting a tweet on the user's behalf. Hopefully you'll find the final steps to be a lot easier to follow and more fun to implement.
They show you how to store the credentials from Part 1 into your session for safe keeping and include a simple form you will use to send a tweet to Twitter. They choose to manually build the HTTP POST request, including the credential headers along with the payload (oauth_consumer_key, oauth_signature, oauth_token, etc).