To enter ReX world you need just few steps:

1. Download the latest release from the "Latest Release" section of from the Downloads section.
2. Run the setup file and install Diablo Expansion: The Rebirth following the installer wizard.
3. Just open your program menu and choose Diablo Exp The Rebirth, the click on "Play The Rebirth".

For further informations or doubts you can browse the FAQs section or the Forum.