If you selected a niche that you have connections with, you should reach out to those people to let them know about the free information you have available. However, when reaching out to your personal network, make sure you’re speaking to those that have interest in your topic. Other peoples' opinions may be interesting, but you really care what actual prospects think.
If you’ve selected your niche wisely, there are also places where members of your niche congregate. These places could be blogs, chat rooms, forums, clubs or associations, or even social media groups. Since you have a valuable lead capture offer available for free, going to these congregation points are a great place to let potential customers know about you and your information.