Well I am not sure that you can call them customers until they buy something. Given the nature of your question I am assuming that you have compelled them to navigate to your site or store front. At this point the answer is simple, but its execution may not be. The answer is to provide a compelling value add narrative to you prospective customers. You may need to figure out who these people are and why they might find value in your product, then convey a narrative that speaks to those needs.