You'll need to login to your bank website and enter the credit limit from there. From there, enter the necessary details like credit limit.
Also, keep in mind that QuickBooks can't track the credit limit of your credit card.
I'm adding this great source where you can find articles that can help you manage your books: QBDT help articles. It includes topics such as reconciliation, track income, and expenses, run reports, etc.
Should you need anything else, don't hesitate to comment below. I'm always around to help. Stay safe and take care always.