Go to the Overview Tab on the trip. Here you can add a video link to the Overview statement for the trip. This will display the video at the top of the itinerary.

Click on the plus sign on the right side of this page, seen below

This will open a box where you can add an Overview Statement to the trip. This is where you should paste the link for the video -

Add the YouTube Video link here by copying the link of your YouTube video and pasting it into the overview statement text field. The link will automatically generate a preview image of the YouTube video.

Preview the updated itinerary by returning to the main itinerary screen and clicking 'Publish' to save your changes. Use the preview option to view the updated itinerary as your clients would see it.