This is to force a user to change their passwords upon (probably first time) login. As a root, change the password expiration date 0 to ensure user change the password in next login.
#/usr/sbin/useradd -g users -c "Fullname + Organization" -m josh
#/usr/sbin/useradd -n -c "Fullname + Organization" -m josh
#/usr/bin/chage -d 0 josh
#/usr/bin/chage -l josh
You can do the same for the existing user. Just issue
chage -d 0 command on the user. User will be prompted to change the password.
You are required to change your password immediately (root enforced)