In short, yes, capture the data you want from your user via a form and then call the API with the data captured on the form as parameters. You will then also need to create a redirect (or callback) page that Twitch will call and pass data back to that you then display to yourself (or your users, or whomever your target audience is).
Although, really there isn’t much your user should have to enter unless you need them to register their own client_id and input it manually onto a form.
From reading your original post, I am wondering, did you obtain a Client ID? If not, you can generate one from your Twitch > Settings > Connections configuration. You will need to provide a URL that Twitch will call back to in order to provide the access token.