First you have to export data i.e. All Masters, All Vouchers as per need. Then if you're importing that data to another Company or Same Company next Accounting Year, open it then import data and make sure you remember the exact name of the Export Output .xls File
Go to GATEWAY OF TALLY then to IMPORT OF DATA >MASTERS In IMPORT OF MASTERS screen,enter the required filename in IMPORT FILE NAME flied and select the required BEHAVIOUR in TREATMENT OF ENTRIES ALREADY EXISTING flied.