Demio does not natively have a paid webinar feature, but there are ways to get around this.
First you would set up the actual payment settings through your preferred payment app (Stripe, Paypal, or even ClickFunnels) and create a package/product that people will buy to get access to the webinar.
Note: You would need to host your checkout page/button on your own website.
Then you would create a zap in zapier to auto register anyone that buys that product. This way when they purchase, they're automatically registered for the webinar instead of you having to go through and add each person manually.
You can check out each zap here: