Setting up GitHub webhooks for an OpenShift build

I tried to set up a github webhook to trigger builds on OpenShift following these docs.

I am confused about two things:

(1) When I create the secret, as prescribed by the above docs, do I need to create one YAML entry or two? Ie. are the following snippets (taken from the above link) supposed to be the same YAML entry?

type: "GitHub"
github:
  secretReference:
    name: "mysecret"

with the second one being:

- kind: Secret
  apiVersion: v1
  metadata:
    name: mysecret
    creationTimestamp:
  data:
    WebHookSecretKey: c2VjcmV0dmFsdWUx

(2) If I query oc describe bc [name-of-my-build-config], I get (all masks of [this] form were added by me)

Webhook GitHub:
    URL:    https://[blabla].openshift-online.com:6443/apis/build.openshift.io/v1/namespaces/[my-namespace]/buildconfigs/[my-build-config]/webhooks/<secret>/github 

So now when I enter this url as a GitHub webhook, what should I replace <secret> with in the above URL? Also, what should I enter in the textbox for Secret on Github (see screenshot below)

I understand that the WebHookSecretKey: c2VjcmV0dmFsdWUx is just an encoded version of the plaintext secret key... So where should I use the plaintext key? Should I also use mysecret anywhere, eg substitute in for <secret> in the above url?

The easiest way to get the full GitHub Webhook URL in OpenShift 4.x is to first get the URL from

$ oc describe bc my-build

...
Webhook GitHub:
    URL:    https://api.example.com:6443/apis/build.openshift.io/v1/namespaces/my-project/buildconfigs/my-build/webhooks/<secret>/github
...

Then, to fill in the <secret> portion of the URL, you get this from

$ oc get bc -o yaml

...
  triggers:
  - github:
      secret: 467ed550-c447-411d-87ad-2d3a3fa81538
    type: GitHub
...

So, for this example, the GitHub Webhook URL would be

https://api.example.com:6443/apis/build.openshift.io/v1/namespaces/my-project/buildconfigs/my-build/webhooks/467ed550-c447-411d-87ad-2d3a3fa81538/github