The Youtube Lightbox is a player widget. To set it up on your site, follow these steps.
- First of all make sure you have the YouTube(lightbox) template set up.
It should be in the list at : Site admin -> plugins -> filters -> Poodll -> templates
If it is not, then its quick to make. This page explains the process for a different player. In your case look for Youtube(lightbox)
https://support.poodll.com/solution/articles/19000080049-how-to-make-a-player-template - Then you need to set up the Youtube(lightbox) to handle Youtube links.https://support.poodll.com/solution/articles/19000077075-choosing-a-player
This page explains how to set the site default player for a file extension. Youtube is a special case and its already in the list of extensions. So you just need to choose the player to handle Youtube links.
The thumbnail will be displayed on a page when Poodll sees a Youtube link in a page. Tp put a link on the page paste the URL into an HTML editor, then select it, or click on it, and choose the link icon on the toolbar. Then enter the url so that its actually linked to the youtube video. That makes the Youtube link.
After that when it is displayed it should look a bit like this ....