First thing is to go to Settings and change the Start Date to 31-May2017. You want Manager’s balance sheet to be the same as the existing one, on the same day. Then enter the Starting Balances for all the balance sheet accounts as they appear on your existing balance sheet.
Here is the balance sheet from the Reports tab. I’ve summed all the assets into one account, and all of the liabilities into one account to keep it brief.
Now do your journal entry, but make sure to date it 31-May-2017. Note that the journal entry does not change the balance sheet: there is a line item that credits Retained Earnings by 107,752.11, but in sum the journal entry debits Retained Earnings by the same amount. However, the journal entry does populate the income and expense accounts.
Here is a the resulting Summary page:
Now you are good to start using Manager. Enter new transactions starting from 01-Jun-2017.