Action Details
Requirements and how-to articles for YouTube's action:

paid action
Create a video ad campaign for YouTube/Google Display Network.

You need this to get it done:

Set up Google Ads account
Create a Google Ads account to be able to create video ad campaigns on YouTube.
Create Video Campaign
Enter the information for your campaign (name, budget, locations etc) and choose a video to use. If non-skippable, must be no longer than 15 seconds. No limit on skippable ads, but recommended less than 3 minutes long.
COPPA Compliance
Note that from January 2020 onwards, personalised ads will not be shown on videos which are aimed at children.
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How-To Articles
A list of useful links for you:

Google Ads Help - Create a Video Campaign
How to create a video ad campaign. (make sure to select "New" instead of "Previous")
Google Ads Help - Your Guide to Google Ads
How to get started with and make the most of Google Ads.
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