Hi there, Rebecca60.
Welcome to the Community. First, I'd like to offer my condolences on the passing of the previous primary of the account. I can show you how to update the primary contact.
To change the contact name for your QuickBooks Online account you'll need to download the Contact Name Change form, enter your information, and then fax or email it along with a couple of other supporting documents.
This article explains the process in detail and provides links for the forms to download: https://quickbooks.intuit.com/community/Account-management/Change-the-business-name-or-contact-name-....
Once you send in the necessary information, you'll receive an email notification regarding the status of the update.
I wish you and your business continued success. Please feel free to contact me if you have any other questions.