How To Do a Mail Merge in Word Using ... - Concord University In Word, open the existing file and press the 'Mailings' tab in the main menu. On the Mailings tab, choose the 'Start Mail Merge' button, a list of different types of documents will drop down (i.e. Letters, E-mail Messages, etc.). choose the kind of merge you want to run. Now choose the 'Select Recipients' button and choose 'Use an Existing List'