Virtual Machine Manager is the desktop GUI for KVM. KVM is as easy to use as any other hypervisor to be honest. RHEL should already have a default storage pool in place so it will just work in my experience, so your images will be stored in /var/lib/libvirt/images.
I have no experience in actually running a Windows install from scratch in KVM (haven't had the need to), however it should be as simple as installing the OS then installing the libvirt drivers, as you would on any other hypervisor.