To set up Opening Nominal, Debtor, and Creditor balances, you would need to complete 3 steps:

1. Create an Opening Balance Journal for all nominal codes, including the Debtor and Creditor Ledger nominal codes (also known as the sales ledger and purchase ledger). You can normally get the list of balances from your previous software.
2. Post the Opening Balances on the Individual Debtor and Creditor Accounts through the opening balance sections under sales and purchases. This doubles the value in the Sales and Purchase ledger and also puts a value in the balance sheet suspense nominal code (999).

3. Create a Journal to cancel out the original Opening Balance values from the Opening Balance Journal and offset it against the Opening Balance amount that has gone into 999. This will then bring the balance sheet suspense code back to zero and restore the correct balances in the Sales and Purchases ledger.