almost 4 years ago - AndrewT - Direct link
Sync Items syncs your Steam games to your Paradox account. It does not do the reverse.

Just paste your Steam Activation code (which we sent to your email, and is in your Paradox Games menu) into the +Add a Game area of the Steam client application, and the game will be available in your Steam Library in that Client to download and install. You can also do this directly on the Steam website
store.steampowered.com

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store.steampowered.com store.steampowered.com
All the best!