Welcome and thank you for posting here on the Community page, @jason6young.
I'm glad to guide you with detailed steps so you'll be able to add the Warranty Date field when creating transactions for your customers.
To be able to add the field, you have to create an additional field to any of your customer's information, then add the field created when recording transactions.
To add the field to your customer's information:
When creating invoices or sales receipts, you can now add the field added by following these steps:
For additional reference about using and customizing form templates in QuickBooks Desktop, read this article.
Get back to me by adding a comment below if you have any other questions. I'm a few clicks away to help. Have a good day!