First time users will be brought to the "Edit My Account" section. There you will enter your email address (this is your log in name), choose a password and choose to receive email notifications.
In the future simply log in using your email address and password.
In the "Edit My Account" area you may notice "Additional Users" boxes based on your subscription. Simply enter their email address.
Your Additional User will receive a confirmation email allowing them to log in, set a password, and subscribe to receive email notifications as well.