This offer's only for UK/EU residents.
If you don't live on those countries you can still get it with VPN/Proxy.

1. To bypass the website restriction, you'll can use the Tunnel Bear / Hola VPN extension, you need to select a UK/EU country.
2. Go to http://store.goldenjoystick.com/free-dark-souls
3. Enter your email on the first field.
4. On the second field you need to enter your Steam ID. ex: http://steamproxy.com/id/mfaliha
5. And on the final field you only need to enter your country, just select the UK/EU. (because you're using Tunnel Bear)
6. Now you just need to confirm and wait 7 days!