1st - Plug In Your Phone to a computer
2nd - Open iTunes & click in the little device that is showing there
3rd - Click in the 3rd Option that iTunes Will show, click it several times until it says UDID, copy it and get in the certificates for testing your iOS Apps
C'est fini (Done) 🎉
We really hope this helps you a lot
If you need anything else, get in touch with us!