you would need to use the PHP mySQL functions, refer to the php manual, http://www.php.net/manual/ref.mysql.php, for information on them, also you would need to know SQL, a good tutorial is, www.sqlcourse.com... after that you would query the database, eg
$result = mysql_query("SELECT * FROM tbl_name WHERE column_name = 'value'");
to put things into a form you would simply echo a forum with variables out..
$z = mysql_fetch_array($result);
$value1 = $z["column_name"];
$value2 = $z["column_name2"];
etc;
echo "
<form method=\"post\" action=\"submit.php\">
<input type=\"text\" value=\"$value1\">
<input type=\"text\" value=\"$value2\">
</forum>";