1. Go to Communications > eMail
2. Hover over your Campaign and click Manage
3. Click Content
4. In the Content view for the eMail enter some text like "View this email as a web page"
5. Highlight the text and click the Hyperlink icon in the icon bars
6. In Step 1. Establish Link choose "Mail Specific Link" from the drop-down menu
7. In the second drop-down menu choose "View as Web Page"
8. Click Submit