If you follow good password management, you won't use the same passwords on mutliple websites. That means it's easy to misplace or forget your passwords. (Okay, if you're like most people, you do use the same password across multiple sites...and you still forget them now and then!)
This video shows you how to get temporary access to your account so you can reset your password.
This video walks you through how to change your password.
Why would you ever change your password? Well, if the site creates your account for you, it will give you a very secure password; but that password will be difficult for you to remember. So you'll want to log in and change it to something you will be less likely to forget.
You do not have to create your own account on this website. The site will setup your account for you the first time you place an order. This vdieo demonstrates the process, including showing when and where the system displays the username and password it assigns to your account.
The video then shows you how you can manually create your account yourself.