moving accounts from another accounts package to sage

Hi,  I hope somebody can help me,  I am changing accounting package and have purchased sage instants,  we are starting using sage from 1st aug 2012 and I need to know the best way of posting openning balances.  do I enter all the outstanding sales and purchase invoices on individually ?, if so seeing as we have just done our vat quarter(end of july) when I come to do the next quarter will it take all the outstanding invoices in to the next vat quarter.

Hopefully some one will be able to help me