Thanks for joining this forum, @frustrated as heck. I know exactly how you feel about the mailing address on your checks being unable to fit in the envelope's window.

To ensure the mailing address is visible through the window envelope, I'd suggest you use the checks envelopes specifically made and guaranteed compatible for QuickBooks checks and forms. Visit the IntuitMarket for more information and to get one. 

For more detailed steps about printing your checks, read through the print checks setup. It guides you through getting your printer and checks to line up. Then, follow the steps to print checks. It also includes a quick video tutorials to guide you in the right direction. 

Feel free to message again if you have additional questions. We're always around to help you more.