So, you'll need instance variables:
User has one to many Devices.
So, the User class will has a List of devices, List devices = new ArrayList(); Put in setters and getters. Device will have an instance of a User. Then add your JPA annotations like usual.
Device has one to one relationship with Token.
Add instance variables - Devices has an instance of a Token, and a Token has an instance of a Device. Then perform the annotation mapping as usual with any one-to-one association.
Here's a good tutorial on mapping one-to-one relations with Hibernate and JPA:
Mapping Associations with the Java Persistence API
There's a discussion of one-to-many mappings on that site as well.
Keep asking questions, and let us know how you're getting along, including code snippets and any errors you have.
-Cameron McKenzie