Upload the downloaded HTML file somewhere it gets a public URL (Netlify Drop, GitHub Pages, or your own hosting), then paste that link below.
Workflow: 1) Fill in the listing and upload photos — the preview updates live. 2) Download the page. 3) Host that one file anywhere public (Netlify Drop is free and takes 30 seconds — drag the file in, get a URL). 4) Paste that URL above to generate the printable QR code for the yard sign.