Path:

Marketing > Campaigns > Drip Campaigns
or
Marketing > Campaigns > Single Email Events

On this page you will have the ability to send a test email for any of your unsent Newsletters or any Drip Campaign by clicking the “Test” button (paper plane icon) in the far right of the individual campaigns/newsletters.

When the test button is clicked a pop-up will appear that will ask you for a "Sample Lead for Dynamic Content." This will use that lead's information to populate any dynamic content you've included in the email, such as the lead's First Name, Choose a lead that is assigned to an agent in your CRM for best results. 

The "Additional Sample Email Address(s)" box is there in case you'd like to send your test to any additional email addresses, e.g. your local admin, or Office Manager. By default, the email you logged in with (your email address) will be emailed the test.