To transfer a captured document from your mobile to scan application you should use the same MobileTwain account on both sides: mobile application and TWAIN driver.
If you don't have a MobileTwain account you can create it through mobile application.
Once you have taken a photo of document a 'Send' button is unlocked and you can press it.
If you don't have an account press 'Register' and enter login, valid email and password