Perhaps a good subtitle would be, "How do I earn a bit of money when I learn how to create a business letterhead in Word." Because you can always find ways to monetize your knowledge (that's what knowledge is for, isn't it?).
Click on the the template. At the bottom right of the dialogue you'll see two options: 'Document' and 'Template'. If you want to use the letterhead to send as a document or letter, choose 'Document.' If you want to edit the template, choose 'Template.' When you choose 'Document,' it gets saved as an MS Word document.