HTC One M8 for Windows - Manual (Page 185)

Restoring a SIM card that has been locked out
If you enter the wrong PIN more times than the maximum number of
attempts allowed, your SIM card will become “PUK-locked.”
You need a PUK code to restore access to your SIM card. You can
get this code by calling Verizon Wireless customer service.
1. On the Phone dialer screen, enter the PUK code, and then tap enter.
2. Enter the new PIN, tap enter, and then reconfirm the new PIN.
Setting a password to help protect your phone
Help protect your personal information and help prevent others from using
your phone without your permission.
You'll be asked to enter the password every time you turn on your phone
or when the phone resumes after it's left idle for a certain time.
1. Swipe down from the top edge of the screen with one finger.
2. Tap All settings > lock screen.
3. Tap the Password On/Off switch to turn it on.
4. Enter your password in both the New password and Confirm
password boxes.
5. Tap done.
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