coopster - 11:57 am on Jul 3, 2012 (gmt 0)

Easy? As in magical? ;)
You need to read in the data from the database and populate your HTML form with the data. Here is a pseudo code sample to give you an idea ...

<?php 
$userid = $_SESSION['userid']; 
$sql = "SELECT firstname, lastname FROM table WHERE userid = {$userid}"; 
execute query, fetch row into variables 
?> 
<form> 
First Name: <input name="firstname" value="<?php print $firstname; ?>"> 
Last Name: <input name="lastname" value="<?php print $lastname; ?>"> 
<input name="formSubmit" type="submit" value="Submit Changes"> 
</form>