Display user info who granted access to my aplication?


I have simple site on which user come ( www.hashtag.rs/index.php ), sign in with twitter and update own statuses. this work 100% like a charm. i want to create something like on this site: http://twtvite.com/ . i want to develop another app for creating twitter events like tweetup’s. when user click on “Yes,i am attending” or “Maybe” i want to they user picture at last always be visible on my site. How to do this?

Thank you.