Sounds like you refer to the recently released Twitch Creator Goals
https://help.twitch.tv/s/article/creator-goals?language=en_US
Which will provide a Browser source to use
Alternatively, if you are building your own, you can consume Creator Goals events
Or if you don’t want to use Creator Goals, you can use EventSub to monitor for new follows and do it that way instead
Your question is unclear, and sounds like a general “How do I Twitch” question rather than a “How do I build a thing on Twitch”