Welcome to the Community space, @GrantBham.
It would be my pleasure to assist you with installing your QuickBooks Desktop 2018 version. However, I recommend contacting the eBay Merchant to obtain the correct email associated with your license and instructions for proper usage. They are the sole source of this essential information.
Please note that the eBay Merchant is the only one authorized to access the information mentioned. Therefore, I recommend that you direct any queries or concerns to their customer service department.
For your future reference in installing QuickBooks Desktop, this article might be helpful for you: Install QuickBooks Desktop.
Don't hesitate to post here in the Community if you have other concerns or follow-up questions regarding the installation of QuickBooks Desktop. Have a good one!
