To pair your Rakuten TV account with your Xbox One, all you need is a Rakuten TV account and, well, an Xbox. If you still don't have a Rakuten TV account, you can do it on the following link:
We recommend you use your email address as username as well to keep thing simple and choose an easy password so that pairing your account with your Xbox is faster.
Once you have a Rakuten TV user, pairing it with your device is very easy. Go to the Rakuten TV app on your Xbox and, once there, go to the "Settings" section and then to the "Pair account" tab, where you will be asked for your username and password.
After entering your user information, click on the "Pair account" button. If everything's correct, you will get a welcome message. This means you are ready to start using Rakuten TV on your Xbox!