The other user need to download Testflight App from AppStore and Register his device.
Then you have tow choices
1) You can add his AppleID in itunes Connect for BetaTest, so there is no need to add his UUID to your devices ..
or ..
2) You register at testflightapp.com as a developer, add his UUID to your devices, and upload the *ipa to testflightapp.com
At both examples the user can start your app