First update the server.
yum update -y ; yum upgrade -y
Install MariaDB and start the server (as root)
yum install mariadb-server
systemctl start mariadb
To check MariaDB status
systemctl status mariadb
The output should be like this
Dec 01 19:06:20 centos-512mb-sfo2-01 systemd[1]: Started MariaDB database server.
To enable MariaDB on boot simply
systemctl enable mariadb
To secure MariaDB install
mysql_secure_installation
Testing the installation
mysqladmin -u root -p version