Uhm, what do you mean with "How do you use NFSv4"? You can either let your CSI-driver/provisioner (1/2) handle it, or create the nfs PVs yourself.
Just make sure your nodes have the needed packages installed.
To be fair, everything authentication related is a mess on NFS.
1: https://github.com/kubernetes-csi/csi-driver-nfs
2: https://github.com/kubernetes-sigs/nfs-subdir-external-provisioner