If you refer to the documentation
It’ll describe the required authentication:
Authentication
- User OAuth token
- Required scope:
channel:read:stream_key
This means you’ll need to generate a user access token, with the scope channel:read:stream_key
Either using:
- OAuth implicit code flow - Getting OAuth Access Tokens | Twitch Developers
- OAuth authorization code flow - Getting OAuth Access Tokens | Twitch Developers
Both flows will require a webpage that redirects the user to Twitch to accept or decline the link.
The first (implicit) gives youi a token good for around 60 days
The second returns a token good for around 4 hours, but comes with a refresh token that you can use to get a new access token.
When you have a token then you can call the Get Stream Key API and fetch the user stream key.
So you’ll need
- to create something that can process the fetching of an access token.
- create something to store the access token (and refresh token)
- use that refresh token as needed to get a new access token
THEN you’ll be able to write some code to then actually go get the access token.