As documented:
curl -H 'Client-ID: uo6dggojyb8d6soh92zknwmi5ej1q2' \
-X GET 'https://api.twitch.tv/helix/streams?user_id=USERID'
Where USERID is the user_id for the channel you are broadcasting to.
or you can use ?user_login=login if you don’t have the user ID