It’s free – you don’t need to pay anything, just create a forum ID which will be password protected.
Your password will be emailed to you. Once you receive that email, you will see a link on it to click on which will take you straight to the forum. You can create a more easily remembered password in your “Profile”.
I suggest that if no-one else uses your computer, you may like to stay logged in. It saves me lots of time!