Simply click on the "Sign up here" button on the home page. It will take you to a page where you can either sign into an existing account or click the "Create new account" tab to register as a new user. You will be asked for your email address, a unique user name, and a few short questions regarding your biking habits and history.
You will also be asked a simple math question. It seems silly, but this feature prevents automatic web search programs from creating unwanted registrations in our system.