To attract more participants, you can start from some free webinars for certain times. Once you can get webinars well prepared, run webinars interactively and show the great value of your webinar, more and more participants will be willing to pay for your entire webinars and then it's a good chance to create paid webinars to monetise your expertise.
Create a presentation you can deliver which is related to that product. The presentation should be helpful and useful, and mostly pure content. If the webinar is going to be an hour long, then you should have at least 45-50 minutes of good, solid content in there before you ever even talk about the product. An exception would be if the entire point of the webinar is how to use that product.
Urgency and scarcity are the holy grail of webinar offers. Pounce on your audience’s high energy and attention by slapping on a sense of urgency or scarcity so they will bite before their next meeting or before some social notification pops up on their screen. What you don’t want to happen is lose a sale simply because an interested prospect who planned to purchase forgot to return.