You should enter balances for each Account as they stood at the end of the previous fiscal year. Use the Transaction register for this task. This information should be available in the Trial Balance report obtained from your old system.
You can enter a single opening balance figure for each Account, or you can divide the opening balance figure into individual postings. This decision may depend on the Account itself.
If appropriate, enter the Transactions for the current year to date, again using the Transaction register.