How to manage certificate signing requests with the Kubernetes API

As I was following this documantation I got this error:

error: resource mapping not found for name: “testuser-authentication” namespace: “” from “STDIN”: no matches for kind “CertificateSigningRequest” in version “certificates.k8s.io/v1beta1” ensure CRDs are installed first

When I tried this script:

cat <<EOF | kubectl apply -f -
apiVersion: certificates.k8s.io/v1beta1
kind: CertificateSigningRequest
metadata:
  name: testuser-authentication
spec:
  groups:
  - system:authenticated
  request: $(cat ~/certs/testuser.csr | base64 | tr -d '\n')
  usages:
  - digital signature
  - key encipherment
  - server auth
  - client auth
EOF

that I took from the docmunation from “Managing Certificate Signing Requests with the Kubernetes API” character.

Please help to solve the problem