Thank you for your interest in trying the beta of Tweetium for Windows Phone!
First and foremost, this is a BETA release, and thus you may encounter problems or incomplete UI. Second, this beta is intended for owners of the current Tweetium app, who can download it for free.
Visit this link on your phone to install the app! Download 2.5 WP8.1 Beta
See release notes and current build # in the store Details page.