Select Steam icon on the website in the pop-up window.
Right after selection you will be redirected to the following page where you need to enter Steam account credentials to proceed.
After you enter all the details, you will be redirected to the page where you need to enter the e-mail for validation.
Right after you click "Submit" the following window will pop-up:
On the e-mail you've entered there will be a message sent to validate your account&
Check the inbox(dont forget the spam folder) and locate the following e-mail:
After you click "Validate now" you will be redirected to the Life is Feudal website and already be logged in with your Steam account linked.