Reset your password. That's the easiest way to get your account back.

1. Go to https://twitter.com/ and click the link "Forgot password?" that is under the login button.
2. You can enter your email address or your username there and you will receive a an e-mail from twitter shortly.
   
3. Click the reset your password button in your email that you received.
4. Type twice a new password for this account.
5. Finally, use this email address and password on your app in order to connect it to the specific account.