To activate the game, you must complete the following steps:

Choose a game distribution system
Rockstar Games
Uplay
GOG.com
Origin
Steam
Epic Games
ElderScrollsOnline.com
Battle.net
Bethesda.net
Rockstar Games
  1. Create a Rockstar Games Social Club account.
  2. Download and install Rockstar Games Launcher.
  3. Log in to your account.
  4. Click on the profile picture of your account in the upper right corner, select "Use activation code."
  5. Enter your code and click "Activate".
Uplay
  1. Log in to your account. If you do not have an account in Uplay, register it by clicking on the "Create an Account" button.
  2. To activate the game in the Uplay client, click on the gear symbol in the upper right corner and select "Activate product".
  3. Enter the activation key and confirm the activation.
  4. After successful activation, go to the "My Games" section to download the game.
GOG.com
  1. Register at GOG.com or log into an existing account.
  2. Go to the key activation section and enter the key received immediately after payment.
  3. After activation, the game will appear in the list and you can download it through the interface of the GOG.com website.
  4. The installation (download) process takes about 10-60 minutes (depending on the parameters of your Internet connection).
Origin
  1. If the Origin client is not installed, download and install it.
  2. Log in to your account or register a new one if you do not already have one.
  3. Go to the "Origin" menu and select "Activate Product Code".
  4. Enter the activation key that you received after payment.
  5. After successful activation, download the desired game and run it.
Steam
  1. If you do not have the Steam client installed, download and install it.
  2. Log in to your Steam account or register a new one if you do not have one.
  3. Go to the "Games" section and select "Activate via Steam ...".
  4. Enter activation key.
  5. After that, the game will be in your Steam library, and you can download.
Epic Games
  1. Log in to the official site of Epic Games.
  2. Go to your account and go to the Enter code section on the left (in the drop-down menu in the Activate code item the key is not activated).
  3. Enter the activation key that you received after payment.
  4. Download the game from the Library section
ElderScrollsOnline.com
  1. Create an account on the official website of the game or log in to the already created one.
  2. On the account page, click on the “REDEEM CODE” button, enter the received game key in the field and click on the “REDEEM CODE” button.
  3. The game is activated, you can download the distribution of the game from the link "Download Game", on the account page of the game.
  4. For technical support, contact help.elderscrollsonline.com
Battle.net
  1. Create a  Battle.net account.
  2. Download and install the Battle.net client.
  3. Log in to your client account.
  4. Select "My Games" from the menu.
  5. Click the "Attach game key" button and enter the activation key that you received after payment.
  6. After successful activation, download the desired game.
Bethesda.net
  1. Log in to your Bethesda.net account.
  2. In the site menu, find the Redeem code item and enter the activation key.
  3. Download and launch the Bethesda.net launcher and log in to your account.
  4. After successful activation, download the desired game and run it.