If you're Uplay game prompts for a CD-Key when you start it you can find it within the Uplay client as follows:
- Select the Uplay client.
- Click your Account name (upper right corner) and select "Account Information":
- Click "My Games" in the left hand column:
- Find the game you're trying to play in your list of games and click the associated "Show Key" link:
- Click the "Copy" link to copy the key to your clipboard (if you're playing the game on this PC) write down the key.
- Paste/Type the key into the dialog displayed when you start to play the game.