There are a number of ways to log into the website:
This is probably the easiest way:
On the right hand side of the Home page is an item that looks like this:
(when you’re already logged in, it will say Log out instead)
Just click on the (blue) Log in link, and it will take you to a web page that looks like:
Enter the user name you were given when you received your welcoming email, or the email address you supplied when registering for the website, and then the password you chose. Click on the Log In Button, and it will take you to the home page of the website: