# Update the kubeconfig file for auth.
aws eks update-kubeconfig --region us-east-2 --name cluster-name

# Login to argocd server through cli
argocd login <argocd_server_url> --password <password> --username <username>

# add external cluster through cli to argocd
argocd cluster add <kube_context> --name <cluster-name>

Note: kube_context format for EKS: arn:aws:eks:<region>:<account_id>:cluster/<cluster_name>