Desktop Environment is not neccessary for Server usage, though. But Sometimes installation or using an application requires Desktop Environment, then build Desktop Environment as follwos.
[1]Install MATE Desktop Environment on here.
[root@dlp ~]# yum -y groups install "Server with GUI"
# install from EPEL
[root@dlp ~]# yum --enablerepo=epel -y groups install "MATE Desktop"
[2]Input a command like below after finishing installation of new packages.
[root@dlp ~]# echo "exec /usr/bin/mate-session" >> ~/.xinitrc
[root@dlp ~]# startx
[3]MATE Desktop Environment starts