Import RKE cluster to Rancher HA

Hi to all,
I have a rancher single install on a dedicated server where I created from the UI a k8s cluster with 3 nodes (This rancher install is on one of these 3).
Now, I created a Rancher HA with 3 new servers and I would like to import the existing k8s cluster.
How should I proceed?
I would like to keep all namespaces and what already exists in the cluster if it’s possible.

If you installed with RKE, you could add a couple more nodes to your config, or take a backup of the etcd db and restore on the new cluster.