Many labels have a QR code attached, which you can take the email to the post office and have them scan that. If you don't have one for whatever reason, you would have to go to a library or find someone with a printer you can use.
You can save it as a .JPG file to a USB memory stick. Places like Walmart, Walgreens and Target have a place where you can print it as a photo. It's often by returns / customer service counter.
