You can use Append to Search to create a list of clients or contacts. Once you select your clients, you can use the Mail merge wizard to produce your labels or envelopes.
In the toolbar, click Contacts.
From the Find Client page, deselect Hide form when only one item found (located at the bottom of the view).
On the Tasks bar, click Clear search.
In the Search bar drop down, select Append to search.
In the Search field, type the first client you want in the list, and select the client from the auto-complete list. The Find Contacts window displays.
Check the correct contact is displayed and click OK. The client is added to your list.
Repeat steps 4–6 until your list is complete.
Press Alt + O for OK instead of using your mouse.
Select the checkbox in the column heading to select all clients.
In the Tasks bar, click Mail merge wizard.
Follow the steps detailed in Creating a mail merge for emails.