Your caption says to comment a word for the guide. This trigger connects that comment to a Flow Builder journey, so the next step can send the promised private reply.
Choose the content and keyword
Select Comments on Post or Reel as the trigger.
Choose the intended post or reel. Use Any post or reel only for an account-wide rule; use Next Post or Reel for upcoming content.
Add the keyword from your caption, such as guide.
Configure Public reply to comments if you also want a visible response under the post.
Add Send a DM, write the resource message, and validate the flow.
Keep public and private replies separate
A public reply can tell someone to check their inbox. It isn't proof that the private DM arrived. Check both outputs when your automation uses both.
If you want the conversation to continue beyond the first private reply, follow the editor's reply-button path. Another automated DM may be unavailable until the recipient uses that supported button.
Test on the selected content
When the automation is active, leave a matching comment from a second account on the intended content. Check that account's inbox and message requests. Then try a nonmatching comment to check the scope.
If you chose upcoming content, an old post isn't the right test. For a post-specific problem, see Fix automation not working on a specific post or reel. Continue with Send a DM from Flow Builder for message setup.