Now that you have an idea, create a one pager that will easily summarize what you believe and who you are. Also include an image that will give testers an understanding of the product or service that you intend to offer. Present the concept statement to a user and listen to and note their response. What do they agree or disagree with? Don't sell the idea or comment, just ask for clarification to get deeper insights.
A large paper or bristol board and writing or drawing materials.