1.    Open the Merge Documents window. 

2.    Right-click and select Add Row.

3.    Type in the Letter Code.

4.    Select the appropriate Module/Access code from the drop-down list.

5.    Select the appropriate letter type from the drop-down list.

6.    Type in a description.

7.    Save.

The Merge Document is added, but you still need to define it. See Define a Merge Document in the Merge Document Definition Window topic.