Adding a Script to the Admin Backend


I want to add a Zendesk Dropbox to the backend of Wordpress for all my subscribers (here is an image if you need to see it:

Here is the JavaScript code that I have to insert:

<script type="text/javascript">
var zenbox_params = {};
zenbox_params.tab_id = "support";
zenbox_params.tab_color = "orange";
zenbox_params.title = "";
zenbox_params.text = "How may we help you? Please fill in details below, and we'll get back to you as soon as possible.";
zenbox_params.tag = "dropbox";
zenbox_params.url = "";
<style type='text/css'>@import url('//');</style>
<script type='text/javascript' src='//'></script>

Where do I have to place this script?

Thanks and be well,