Get my own subscribers from a request? Where to start?

API
8

Thats step 2 of oAuth

They come back to your site with a code

You then make a HTTP Post to exchange the code for a token.

That gives you a JSON blob with the actual access token AND the expires time for that token

Step 3:

POST https://id.twitch.tv/oauth2/token
    ?client_id=<your client ID>
    &client_secret=<your client secret>
    &code=<authorization code received above>
    &grant_type=authorization_code
    &redirect_uri=<your registered redirect URI>