It is very easy to start a website and advertise a product. I agree that you have also sold a lot of your products. That is good. But how was the customer experience ? Did you sell to some big names ? If both of them are positive, you need to flaunt it. It is really going to help you with new conversions
There is a free WordPress plugin called Easy Testimonials which can help you with this
Easy Testimonials is an easy-to-use plugin that allows users to add Testimonials to the sidebar, as a widget, or to embed testimonials into a Page or Post using the shortcode. Easy Testimonials allows you to insert a list of all Testimonials, output a Random Testimonial, or display a slideshow of Testimonials anywhere on your website.
I would suggest that you take proper permission from your customers before adding those testimonials. After all, your product is their secret weapon. They might not need to shout about it in all cases.