Login from an app

Hello,
I’m trying to use this plugin with an app and with WP-REST-API. I followed the three steps (authorize, request_token, request_access), but the authorize just return a html page to login. Does there is a way to generate the auth_key in another way? Could I save the access_token permanently in my app?

Thanks…

https://ww.wp.xz.cn/plugins/oauth2-provider/