The following steps are intended for the HTC Arrive running any Android software.
Tap the Right Arrow
Dial ## 675 #
Enter the MSL, then tap OK
Enter MDN, then tap OK.
(Note: The MDN is your mobile number. Refer to your activation email or log into your online account to find the MDN.)
Enter the MSID, the tap OK
(Note: Refer to your activation email or log into your online account to find the MSID.)
The phone will restarted and then it will be ready for use.