To change the password for a user, when logged in as that user, from the command line enter:

** sudo passwd pi ** — (make sure you use the correct username, pi is just for the example)
you will then be prompted to enter, then re-enter the new password

//**

      $ sudo passwd pi
      
      Enter new UNIX password:
      Retype new UNIX password:
      passwd: password updated successfully

**//