A family of Microsoft word processing software products for creating web, email, and print documents.
The only setting you need to change is the size of the frame. This is best done in the Word application itself rather than in the Envelopes and Labels dialog. You can use Add to Document in the Envelope dialog, but then you'll have to divorce the envelope from the document, which is a nuisance. Instead, just create a document the size of the envelope (depending on your printer, you may be able to find the envelope size on the Paper tab of Page Setup.
You can then either apply the Envelope Address style to the default blank paragraph and fiddle with changing the size of the frame or, more simply, just use the usual paragraph settings (Center, Spacing Before) to place the text on the envelope.