I'd be glad to walk you through with the process, junehoustoncorp2.
To make the current account as sub-account, you can follow these steps:
- Go to Accounting > Chart of Accounts.
- Find the account and select the drop-down arrow next to the View register link.
- Choose Edit.
- In the Account window, select the parent account from the Is sub-account drop-down menu.
- Hit the Save and Close button.
Here's a sample screenshot for a visual guide:

I'm also adding this article for reference: Create sub-accounts in your chart of accounts in QuickBooks Online.
Please leave a reply if you have any additional questions or other concerns. Thanks.