To activate TESO (Tamriel / Morrowind) codes, please follow these steps:
1. Visit http://account.elderscrollsonline.com .
2. Log into your Elder Scrolls Online Account, or create one if needed.
3. Select Redeem Code on the My Account page.
4. Enter your game activation code first!
5. Enter any additional codes you might have.
Download the game client by clicking either the PC or Mac download link on your account page. Follow the instructions to install the client and make sure you pick your preferred megaserver (Europe or North America) during the installation process.
In case you experience any problems, please visit the official The Elder Scrolls Online knowledge base or contact customer service. English: https://help.elderscrollsonline.com