In Word, choose File > New > Blank Document. To perform a Letter mail merge in Microsoft Word Make sure the 1st row in Microsoft Excel is your header row when doing a mail merge in Word. If you were sending your customers a letter, the Excel file would include Company Name, First Name, Last Name, Address, etc.
One of the easiest data sources to use is Microsoft Excel. It contains the records Word pulls information from to build the addresses for the labels, letters, or envelopes. The mailing list can be an Excel spreadsheet, a directory of Outlook contacts, an Access database, or an Office address list. To perform a mail merge with Microsoft Word, you need a data source or a mailing list.