Yay, I googled about this topic, wonderful, I finally did it.
To install Gnome GUI on your Cent OS 7 server, do this commands:
# yum group list
Then:
# yum groupinstall "GNOME Desktop" "Graphical Administration Tools"
And then this command to make the computer starts using GUI on next boot:
# ln -sf /lib/systemd/system/runlevel5.target /etc/systemd/system/default.target
Then reboot it:
# reboot
Coool! That’s all.