Download the kubeconfig

To download the kubeconfig, navigate to Manage Cluster and select the correct cluster. On the top right you can find a button Download config:

Download config button in the top right corner

The token in the kubeconfig gives you full admin rights within the Kubernetes cluster.
You can change the admin token by revoking the existing one on the cluster detail page. Already downloaded kubeconfigs are not valid anymore then and need to be re-downloaded:

Revoke the admin token