I've been provided with a client_id and a URL where I can get a secret to it, so these would be pre-defined.
In my understanding I should go to Authorized applications under Integrations part and administer the application.
I don't know. We cannot investigate customer data from the forum.
If you are clicking on Authorized Applications tile (and not the link/URL you mentioned) and getting this screen, this is likely a permissions issue.
Customers can modify existing/pre-defined roles so I don't know what permissions your user has.
I would suggest to:
Logout and then login again (in case you didn't since the roles were granted to your user)
If you are willing to troubleshot, you can open your Chrome Developer Tools - Network tab, open/click the Authorized Applications link and check if a request to Genesys Cloud gets a 403 or other error back (403 should imply you are missing a permission).
or you can open a ticket with Genesys Customer Care as they have access to your environment.
As a note, for configuration related questions, please post to the Genesys Cloud Community forum.
The Developer forum is meant for questions related to API and SDKs.