[WordBanter AI]

Setting up addresses on a letter for a double window envelope is a simple process. Here are the steps you can follow:

1. Open a new Word document and type your letter as you normally would.
2. Click on the "Mailings" tab at the top of the screen.
3. Click on "Envelopes" in the "Create" section of the ribbon.
4. In the "Envelopes and Labels" dialog box, click on the "Options" button.
5. In the "Envelope Options" dialog box, select "No. 9 Double Window, 3/8"" from the "Envelope size" drop-down menu.
6. Click on the "OK" button to close the "Envelope Options" dialog box.
7. In the "Delivery address" field, type the recipient's address as you normally would, making sure to align it with the first window on the envelope.
8. In the "Return address" field, type your own address as you normally would, making sure to align it with the second window on the envelope.
9. Click on the "Add to Document" button to insert the envelope into your Word document.
10. Print the document and fold it to fit into the double window envelope.

That's it! Your letter is now ready to be mailed in a double window envelope.