Accounts' historical balances aren't required
No. You're not required to enter historical balances for any of the months previous to your conversion month, but you might find this information useful if you want to compare the current year's account balances with last year's on balance sheets and profit and loss statements.
(Once you begin using MYOB Accounting Plus, balances for your conversion month and subsequent months are updated automatically whenever you record sales, purchases and other transactions, so no entry is required for those months in the History view of the Account Information window.)
For detailed instructions on entering historical balances, see To enter detail accounts' historical balances.