Upwork webinars are usually hosted by Upwork Ambassadors and the Upwork Community team. Topics range from getting started tips for new freelancers to business growth webinars for experienced freelancers and curated expert talks.
You can find a full list of previous webinar recordings here. Note, you can access the recording by clicking on the registration link. After filling out the registration form with your name and email, you will be redirected to the video of the recording.