Need fixing generic posting on facebook

This is quite easy to do if you have access to edit the header of your website. All you need to do is enter the appropriate Open Graph metadata for each page.

ie (and taken steaight from http://ogp.me/):

<html prefix="og: http://ogp.me/ns#">
<head>
<title>The Rock (1996)</title>
<meta property="og:title" content="The Rock" />
<meta property="og:type" content="video.movie" />
<meta property="og:url" content="http://www.imdb.com/title/tt0117500/" />
<meta property="og:image" content="http://ia.media-imdb.com/images/rock.jpg" />
...
</head>
...
</html>

If you have entered the appropriate data, and you’re not seeing the changes right away – try de-linting the URL.

Edit: There are many good wordpress plugins that can handle this too. Yoast is my personal favourite, but there are more out there.