Can anyone provide help with connecting to Workfront via OAuth JWT

I have thoroughly read the article here: 

https://experienceleague.adobe.com/docs/workfront/using/adobe-workfront-api/api-notes/oauth-app-jwt-flow.html?lang=en

Unfortunately, I have found it quite hard to get this working in the real world, an example of what the token would look like would be really helpful. 

To test this myself I used https://jwt.io/ to help. 

I set the Algorithm to RS256. 

In the payload I added the following data:

{

  exp:  1693469597  - Expiration Date (Epoch time)

  iss: "abcd"   - Customer ID (from OAuth config)

  sub:  "abcd"    - UserID (from OAuth config)

{

However, I get a message that my token is invalid, which I assume is something to do with how it is signed as I've not provided the Public key ID anywhere. 

I generated a public/private keypair which is stored in Workfront, but not sure what to do with it.

Is anyone able to provide any assistance?

Thanks,

Rob