Step One: Select the proper tool

Click on 'Marketing' link under the 'Website' heading of the Control Panel menu. 

Step Two: Select New Arrival Notification

Click the 'New Arrival Notification' section.

Step Three: Open Email Template Tab

Click on the 'EMAIL TEMPLATE' tab.

Step Four: Make updates

Edit your new arrival 'Email Template'.

Step Five: Don't forget to save

When you are finished, scroll up/down to click the 'SAVE' button.