How do I. Unlock my ZTE 831 CHAPEL

[Cheryl H Janis]

It says network lock

 

[Rukbat]

That means that it's locked to the network it was made for. All phones are. To get the unlock code, it has to still be on an account on that carrier, or you'll have to find someone (usually on eBay) who sells unlock codes and buy one for your phone. (And hope it has the radio bands that your current carrier uses - different carrier's phones have different 4G bands.)