Do you want to use a video in the product image slider? Which can. For this you have to do a few things.

1) Make sure you have the "extra template data" turned on. Don't have this? Then follow to step 2.
Active? Go to step 3.

2) Activate additional template data, you do this by navigating to: Settings -> Workflow -> activate extra template data

3) Navigate to Products -> "product" and see if the template data is active, if this is active you will see the following (all fields are probably empty):
​

4) Find the YouTube, vimeo or other online video you want to use.

ALWAYS USE THE EMBEDDED URL!
​
For YouTube you can use the following guide

5) Click on "share", a popup will appear, then click on "embed".
​
​

6) Copy the part containing the link, this is always after the src="

7) Paste this URL into Data 03.
​
​

Another option to get the correct link for the video is as follows:
1) Copy the URL of the video from the address bar (https://www.youtube.com/watch?v=nzv1Y-NUiG0)
2) Change the URL of the video by replacing the part after the .com "/ watch? V =" with "/ embed /"