Pls, I needed help on how to unlock my Mtn Heuwei Modem.

Although, have generated my unlock and flash code online but d modem is not asking for unlock code by default when inserted with other Sims type to a PC. I downloaded an app named Heuwei Modem code writer by Sagmasterz, and it is displaying error when unlock and sometimes it won't read d cms port.
Apart from d app, I didn't no how else to get this done.