I got your back to ensure you'll be able to enter the beginning balance seamlessly, @juliedavidson040.
Let me provide some details on how you can achieve your task.
In QuickBooks Online (QBO), when adding the beginning balance of your credit card, you can enter the latest amount and follow the date you opened the account. However, if you've had the account for a while, you can use the balance from the next bank statement. Also, since this is the money you owe, you can enter it as negative.
Once settled, please refer to this article on how you can enter the balance: Enter and manage opening balances in QuickBooks Online.
Then, to make sure that your account match your real-life credit card statement, it's best to perform the reconciliation process every month.
I'm always willing to assist you in case you have any other concerns about adding the beginning balance of your account. Just post a comment below and I'll get back to you as soon as possible. Keep safe and have a good one.