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.
You can do this through statistics or survey results from your existing customers. Imagine the conversion capability of a statement like, “Seventy percent of customers using our product shaved 10 points off their golf game within a month!” You can just hear them clicking your CTA. Just be sure not to make any outrageous claims—especially income claims. You want to preserve their sense of trust in you.