It's easy. Click on the green 'Sign in through STEAM’ button. Steam will ask you once to validate. Steam Signature will then use the details in your Steam ID to make a Steam signature. You can use it across forums or as a Twitch signature.
Yes! Steam Signature uses the the Steam OpenID software that Valve built to allows users to log in to sites. Steam only gives us two things: your publicly available Steam ID and your current Steam friends handle. It does not give us your username, password, or any other sensitive info. We can’t access your games.
No. Not for doing this. Steam sign in does not to your games or your Steam account directly. It only grabs publicly available information.
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