Use apt-get or yum to install firewalld.
~]# apt-get install firewalld ~]# yum install firewalld
The ps command can be used to determine if your system is using init or systemd. If PID 1 is init, then you will use the service command. If PID 1 is systemd, then you will use the systemctl command.
If your system is using systemd, use the systemctl command to start and enable firewalld.
systemctl enable firewalld systemctl start firewalld systemctl status firewalld
chkconfig firewalld on service firewalld start service firewalld status
Now you can start configuring firewalld.