Holding a 5k is hard work, but it pays off. You have to do many things in order to hold one. You have to get a space large enough to hold the desired number of people, if you close down roads, get permission to close them down, and police and/or signs to keep runners on the right path. It’s also wise to have maps and have refreshments, especially water. Here is a link to a site that can help you run your own 5k:
https://www.active.com/running/articles/how-to-organize-a-5k-a-guide-to-planning-your-first-race You can also collect donations for an organization from people who sign up for your race.