This is a fresh install of RHEL 7.5
First install the packages as shown below.
yum install qemu-kvm libvirt
Now install the additional recommened virtualization packages
# yum install virt-install libvirt-python virt-manager virt-install libvirt-client
Now restart libvirtd
# systemctl restart libvirtd
Now you should be able to launch virt-manager from your remote machine and add a connection to your new virtualization host.
Special note. Make sure that you disable NetworkManager
# systemctl stop NetworkManager # systemctl disable NetworkManager