I don’t have any examples to hand, as the docs themselves are pretty self-explanatory.
- Send user to Twitch to request permission from them
- The user is sent back to your server with a code in the querystring if they accept
- your server exchanges the code for access and refresh tokens.
For specifics on how you create a web server to handle steps 2 and 3 there are plenty of tutorials on Google, or YouTube, for most programming languages that can host web servers and make HTTP requests.