They can create the USCIS account but to have their case attached they will need an Online Access Code that comes with the notice. They input their code on the created account and it pulls their case.
Here is what is written in the notices they can get to step 2 of this instructions without the code. Good luck!!
Welcome to USCIS!
Thank you for your recent submission. We have created a USCIS Online Account for you. With this account you can:
• check the status of your case.
• sign up to receive email notifications and text messages.
• manage your account preferences and contact information.
Log on and confirm your account within 90 days.
To access your account, please follow the steps below:
1. Visit us online at https://my.uscis.gov/account
2. Select "Create a new account" on the right side of the screen, and follow the on-screen instructions for creating a new account in order to
login to the system.
3. Select "Add a paper-filed case."
4. Enter your "USCIS case receipt number" and select "Add case."
5. Enter your "Online Access Code" (found on the upper right side of this notice) and your "Date of birth" in the fields provided.
6. Select "Confirm case."
NOTE: Your Online Access Code will expire 90 days from the receipt date listed at the top of this letter. We will continue processing your
application regardless of whether you access your USCIS Online Account. We strongly encourage you to confirm your USCIS Online Account
as soon as possible and then use it in the future as your preferred method for interacting with USCIS. If you do not access your account before
your code expires and you wish to access your account, you will need to request that we reset your access code. If you have questions about
how to confirm your USCIS Online Account or to request that we reset your access code, please visit the USCIS Contact Center at uscis.gov/
contactcenter.