Select the copy and select the
Edit
button on the toolbar. A new window opens that lets you add and edit the text. You can edit the existing letter, or compose a new one, and can copy text from another application, such as Microsoft Word. (Text pasted directly from Word may not retain the original formatting.)
To add an image, such as your logo, select the insert image icon. You can drag the image into the box that opens, or click into the box and navigate to the image location on your computer.
To add mail-merge tags, position your cursor where you want to place the merge field. Select the small arrow next to the mail merge icon

, then select the merge field from the list.