To get the embedded code for your ExactTarget email:
In your Eventable dashboard, go to the Events tab
Click the Share Event button for your specific event
If you haven't already, select HTML as your email type
Select ExactTarget from the dropdown menu
Copy the embed code
To paste the embedded code in ExactTarget:
For the add-to-calendar buttons to work, your Email creation method has to be either Template or HTML
If you are using a Template, select HTML from the left hand panel, under the Content tab
Drag the HTML block into the left hand panel
Paste the embed code (Control+V if using Windows, Command+V if using Mac) and click Done Editing
If you are using a HTML email, paste the embed code directly.
Preview your buttons in the email by clicking Preview and Test