added verbiage and screenshots for new campaign preview modal

source/User_Guide/Marketing_Campaigns/Campaigns/index.html

@@ -129,16 +129,26 @@
 Preview Your Campaign
 {% endanchor %}
 
+<p>
 It is good practice to look at your campaign on a couple of different screen sizes. In order to expedite this process for you, we have provided a desktop and mobile preview for you. At the top of your screen you will notice three icons that look like the following:
 
 <img src="{{root_url}}/images/templates_8.png" alt="Desktop Preview" /> is the desktop preview option. It will show you what your users will see when looking at your email through their desktop email application.
 
 <img src="{{root_url}}/images/templates_9.png" alt="Mobile Preview" /> is the mobile preview option. It will show you what your users will see when looking at your email through a mobile email application.
 
 <img src="{{root_url}}/images/templates_10.png" alt="Text Preview" /> is the text preview option, also known as plain text. It will show you what text-only users and screen readers will see when they look at your email.
+</p>
+
+<p>
+You may also preview any campaign listed on the Campaigns page. Simply click the Action Cog next to the campaign you would like to preview, and select Preview. You will be shown a small window displaying both mobile, and desktop, formats.
+<br />
+<img src="{{root_url}}/images/campaign_dropdown_preview.png" />
+<br />
+<img src="{{root_url}}/images/campaign_preview_modal.png" />
+</p>
 
 {% info %}
-While the preview functionality we provide will cover many use cases, it will not render the same as all mobile devices or desktop email clients. We recommend you use programs like <a href="https://litmus.com/">Litmus</a> to check that your email renders appropriately across all devices and clients.
+While the preview functionality we provide will cover many use cases, it will not render the same on all mobile devices or desktop email clients. We recommend you use programs like <a href="https://litmus.com/">Litmus</a> to check that your email renders appropriately across all devices and clients.
 {% endinfo %}
 
 {% anchor h2 %}
@@ -194,7 +204,7 @@
 {% endinfo %}
 
 {% info %}
-Clicks can not be tracked in A/B test campaigns. 
+Clicks can not be tracked in A/B test campaigns.
 {% endinfo %}
 
 <img src="{{root_url}}/images/link_tracking.png" alt="Link Tracking" />