Ok - so you should have a few tables. Users, BlogArticle, and Comments. Then when someone clicks on the link on the blog it would go to say comment.php?blgart=1 what that would say is go to the comments form page and add a comment for blog article 1. Then after they submit it would go to the comments table. The what you would do is in php create a script that might have the following (depending on how the table is setup)
$query = sprinf('Select * from comments where blogid = ', mysql_real_escape_string($blogid))
$results = mysql_query($query, $db)
while($row = mysql_fectch_array($results, MYSQL_ASSOC)
echo "<div id='comment'>";
echo "<h3>$row['name']<h3>"; // This represents the comment name
echo "<p>$row['comment']</p>; // this will output the comment left
this is a rough outline and should be expanded on but I hope that is what you had in mind.