I assume you are talking about the redirect URI which is required when registering your application on Twitch?
If this is true then redirect URI should be localhost when testinghithis your application (can be changed later on). After when your application is about to go live you should use a url from your website which the user is redirected to after authorising their account. This will pass in the access token and other information to the url so it can be used by your application.