How to add the UDID to the testFlight Portal

Hi one of our team members wants to add their device to the testFlight account, I have sent the Invitation from the portal and they have accepted It, and I need UDID of that device for the provision profile, they should send it manually?or TestFlight Portal will fetch their UDID If they just accept the invitation ?

Solution

Once people(Tester) accepts the invitation they get a mail from testflight with subject Get Started. If invitees click on the get started and completes all the required step successfully you will get a auto generated email from Testflight with subject line XYZ added a device and the body of the mail contains the following details.

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Then you can add this device id in provisioning profile manually. The only thing is "invitees must use his/her mobile device for opening all the mail from testflight".