There are two ways you can preview your Product. This will also help you in testing videos, attachments and content you've uploaded.
Method 1: Main Page of your Product
*****Important - Make sure that your Modules and Sessions are Live to do a preview.
Just click the Preview Product button. It will give you a preview of your product from the very first Module and Session.
Method 2: While editing your sessions
While editing your Sessions, just click the Preview button at the very top. This will let you preview the Session you're currently working on.