To perform a mail merge, click Start Mail Merge on the Mailings tab, and then click Step by Step Mail Merge Wizard.
The wizard opens on the right of the window in a task pane. The task pane can be moved (undocked) by clicking the title bar and dragging it to a new location. You can also resize it by dragging a resize handle on the sides of the task pane.
To use the mail merge, follow the prompts and click Next at the bottom of the pane to step through the wizard (or Previous if you need to go back to an earlier step).
In Step 1, the wizard opens with a question. It wants to know what type of document you want to merge information into.
Click Play above the illustration to see how to open the wizard and select Envelopes as the document type.