Find content
The steps I would take are:
1. Post a thread of Nerfhaven. Which you've done already, good work 
2. Post a comment on r/nerf. Also search through the post history for North Carolina and Durham to see if anyone else has posted about it, and message them directly.
3. Search Facebook for any local nerf groups. If one does not exist, create it. You want the group to have a very generic and searchable name, so that people can discover it - such as North Carolina Nerf, or Durham North Carolina Nerf. Once a group is created, people will start stumbling on it and sending you messages, so be sure to respond to those.
4. If you know even one other person, host a war and post the event across multiple social media outlets. You may actually have some randos show up, people who saw your event but never messaged you. The majority of people online lurk, but they are real and present.
There is a lot of diffuse interest in nerf wars out there, and so you have to take actions to coalesce it into a community of people who are actively engaged. That's where you have to just "fake it till you make it", host very tiny wars and post invites and information on a lot of online social platforms. Eventually one person will come, and then three, and then six... and at some point you'll actually have a local community of people who are actively participating. The only way to do that is to apply some elbow grease, and to believe in the project even when it seems like you're spinning your wheels.
