Now that you understand the purpose of Self Service and you know where to find where, you want to get started. Depending on your situation, you either want to start from scratch with a new stream as indicated in the image below, or you want to consume the data on an existing stream.
Create an application in Self Service that represents your actual producer/consumer application (which is deployed somewhere)
Configure application principals for your application, so it can be authorized to produce to or consume from the stream. Note: you need to do this for every environment the application is running.
Request stream access, so your application can actually produce or consume.
Before creating a new stream (topic) most likely a schema must be discussed and finalized. This is currently outside the scope of Self Service. Once schema is developed and available for use, you can proceed with below steps to create a new stream in Self-Service.
For this purpose, you need to Create a private environment
Refer to Authorizing stream access
See here how to do that.