Slider Plugin code for Index.php file help

H again everyone
I am creating a website using WordPress and I’d like to have a Slider to show up at the top of my pages right below the navigation bar but above the sidebar and body.
I’ve downloaded and activated a couple Slider plugins ( Smooth Slider, Vslider and Nivo Slider) and I’ve looked it up and some say I should insert this code into the Index.php file of my theme. Here’s the code:

<?php if (function_exists(‘get_smooth_slider’)) { get_smooth_slider(); }?>

I’ve setup my sliders and tried inserting this code right under the “get header” code in the Index.php file of my theme but nothing shows up on my page. I’ve tried this with each slider (changing the code accordingly) and it still doesn’t work. I was wondering if anyone knew what I was doing wrong. Like am I placing the code in the right place in the Index file or is should I be placing the code in a different .php file or is the code even typed correctly?
If anyone could help me with this it would be very much appreciated. Thanks again everyone.