If you want to add Simple Nivo Slider to a post you can use this shortcode [snivo]
— this is from the instructions at http://wordpress.org/extend/plugins/simple-nivo-slider/installation/
If you want to place it on your homepage … you can edit your theme files (probably content-single.php) and this code <?php if (function_exists('simple_nivo_slider')) simple_nivo_slider(); ?>
The simplest … is create a Page (WordPress Admin > Add New Page) and add the [snivo]
then go to WordPress Admin > Settings > General and Choose your new page
see also: http://codex.wordpress.org/Creating_a_Static_Front_Page