Go to Twitch and log in to your account
Open Creator Dashboard
Click Settings
Select Stream
Turn on Store past broadcasts
Save your changes
Stream normally on Twitch
Wait for Twitch to automatically save your broadcast after it ends
Go to Video Producer to find your saved streams
Download or highlight the saved stream if needed
Note that Twitch saves past broadcasts for a limited time unless you are a Partner, Affiliate, or Turbo/Prime user
Use external recording software if you want a permanent local copy