Your site has one (1) user by default, and that would likely be yourself or whoever created the site. Here, you may add, delete, and assign or change user type. This section becomes important when deciding who has the necessary permissions to edit your website.
When a user needs to change their password, or is not able to login to their SimpleUpdates website, they need to reset their password.
At the bottom of every page is the Login / Customize link, and clicking this takes you to the login window. On this screen there is a reset password link (shown in red on the image.) This will help you reset your password. You will get an email from this process with a link that you can use to enter a new password.