You can create a journal entry to record your opening balance. Let me guide you how.
Go to + New. Then, Journal Entry.
Enter a Journal date that's before the oldest transaction already in your account. This is your opening balance date.
On the first line, select the account you want to enter the opening balance for. Use your bank statements to enter the opening balance. It should be the balance for your real-life account on the opening balance date:
For assets (savings and checking) and expense accounts: Enter the opening balance in the Debit column.
For liabilities, equity, and income accounts: Enter the opening balance in the Credit column.
For Accounts Payable: In the Name field, select the suppliers you owe money to. Enter the amount as a credit if you want to increase the balance. Or enter it as a debit if you want to lower the balance. You can create separate lines for each supplier. The total amount should equal the opening balance.
For Accounts Receivable: In the Name field, select the customers who owe you money. Enter the amount as a debit if you want to increase the balance. Or enter it as a credit if you want to lower the balance. You can create separate line items for each customer. The total amount should equal the opening balance.
On the second line, select Opening Balance Equity in the Account column.
Write a note in the Description field so you know what the journal entry is for.