To turn on the firewall in RHEL, use the command: `sudo systemctl start firewalld`.

To enable the firewall on RHEL for live servers, follow these steps: 1. Open the terminal on your RHEL server. 2. Gain root access by typing `su` and entering the root password. 3. Start the firewall service by executing the command `systemctl start firewalld`. 4. Enable the firewall to start automatically at boot with the command `systemctl enable firewalld`. 5. Check the status of the firewall to ensure it is active by using `systemctl status firewalld`. 6. Configure the firewall rules as needed using `firewall-cmd` commands, such as `firewall-cmd --add-service=http` to allow HTTP traffic. 7. Reload the firewall to apply changes with `firewall-cmd --reload`. Ensure that you have configured the necessary rules to allow traffic for your live server applications before enabling the firewall.