The {{{Campaign:EmailLink}}} merge tag is the magic code that you'll use any time that you'd like to have your subscribers be able to view your newsletter in their browser.

This inserts into your message a "View this message in your browser" option.

This merge tag behaves similarly to the Unsubscribe merge tag in that it's best to use the pulldown merge tag option from within the WYSIWYG or Drag & Drop Editor.

But if you wanted to copy and paste this merge tag into your campaign then follow the following steps

Step 1: Click on the HTML icon

A new screen will pop up. 

Step 2: Copy & Paste the following code into that popup window

 <p>Having trouble reading this message? <a href="{{{Campaign:EmailLink}}}" target="_blank">View it in your browser</a></p> 

Step 3: Scroll down and click update.

The View it in your browser functionality will now be included in your message.