How to put html metadata lines in a landing page?

Hello, i wanted to add a html metadata line or two in the landing page. Spoke to 2 agents but to no avail. I could not find any option or settings aswell. The line is < meta property=“og:image” content=“url” >

	<meta charset="utf-8">
	<meta http-equiv="x-ua-compatible" content="ie=edge">
	<title>Test Landing Page</title>
	<meta name="description" content="">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	**<meta property="og:image" content="url"/>**