PLEASE HELP MEH

I have been looking through the forums tryn to figure out how to get the “add Thumbnail” option to show up in the Post Edit Screen. What I have found is that you have to add a certain line of code to your themes functions.php file in order for it to even show up. Well oddly enough the theme I am using already has that line of code inside the function.php. It looks like this:

<?php if ( function_exists(“add_theme_support”) ) { add_theme_support(“post-thumbnails”); } ?>

And this is the theme I am using:

http://newwpthemes.com/wordpress-theme/contrive/

However the line of code that the WordPress Codex tells you to add looks a little different:

<?php if ( function_exists( ‘add_theme_support’ ) ) {
add_theme_support( ‘post-thumbnails’ ); } ?>

I have tried using both of these codes and they both don’t work. Do you need to place them in a certain position inside the functions.php? And yes I have tried using featured image already and that doesn’t work. This theme allows for a featured posts slideshow on the homepage and in order to get a picture to show up on that slide show it has to be a thumbnail.

Here is exactlty what the theme options says about the image on the slide show:

How to add images to your featured posts slideshow?
» If you are using WordPress version 2.9 and above: Just set “Post Thumbnail” when adding new post for the posts in selected category above.
» If you are using WordPress version under 2.9 you have to add custom fields in each post on the category you set as featured category. The custom field should be named “featured” and it’s value should be full image URL. Click here for a screenshot.

In both situation, the image sizes should be: Width: 610 px. Height: 320 px.

Please help if you guys could. I really do not know much about php.