Here are the steps for how you would set you account up to be able to link across different devices:
1. From the World Map, go to the SETTINGS Menu
2. Press the ACCOUNT button in the bottom right of the Settings Menu
3. Now press the REGISTER THIS DEVICE button. You'll need to provide us with your email (don't worry, we're not planning on using it to spam you!)
4. You will receive an email in your inbox that has a link. You must click the link to verify that your email address is correct.
5. Now that your device is registered, you can get your password! From the Account Menu once more, press the PASSWORD button to get your password. Write this down and don't lose it!
6. You're all linked up!
Please note that Xbox & PS4 accounts cannot be linked, they are standalone.