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

Create a Community text post. (If your account has at least 1000 subscribers.)

You need this to get it done:

Community Text Post
Write a Community Text Post.
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How-To Articles
A list of useful links for you:

YouTube Help - Engage viewers with Community posts
Information on how to create Community posts.
Link missing here or found errors? Improve How-Tos