I screwed up plugin editor

I was attempting to place a shortcode (<?php echo do_shortcode(“[viralsignups_form align=“center”/]”); ?>) into the functions.php file for the plugin editor for this “coming soon” plugin, and when I clicked the update file button, my entire wordpress got screwed up.

Now anything I click, gives me a blank page. Could anyone please help me in figuring out how to reset or reverse what went wrong with the plugin.

Thanks kindly in advance