after creation of RKE cluster, what should I do to use vSphere CSI ??? Do I need to go RKE cluster\App, and choose CSI helm chart and install it ??

Seems so: https://docs.ranchermanager.rancher.io/v2.5/how-to-guides/new-user-guides/kubernetes-cluster[…]cloud-providers/vsphere/configure-out-of-tree-vsphere