It's easy.
rpm --import https://packages.icinga.com/icinga.key
yum -y install https://packages.icinga.com/epel/icinga-rpm-release-7-latest.noarch.rpm
yum -y install icinga2
yum -y install nagios-plugins-all
service icinga2 restart
And then execute the agent script on the client and restart icinga2 on the client.