Trying to change featured image from 180×180 to full width on home page

Find the post thumbnail reference in your homepage template, or content-{single?}.php -whatever is generating the 180×180 image and change it to:

<?php the_post_thumbnail( 'full' , array('class' => 'home-page-thumbnail') ); ?> 

and add the following to your style.css file:

.home-page-thumbnail { clear:both; }