No. After your event you send a short recap: a few photos of the product being used at your moment, and a couple of quick questions.
The recap goes to onbrand and to the brand. Approved photos can also show on your public profile, and brands may use them in their ads (Terms, section 4(c)). It is not a social media post. You do not need to post anything on your own accounts. A video is optional.
Related: What Is Verification?