A benefit concert sounds like an amazing idea. You could have yourself and a few other local musicians perform and it would be a lot of fun. First, make sure you have a place to do it. Look into parks and small (preferably outdoor) venues in your town that aren't overly expensive to use. A large park in your town would be an ideal spot. Email your town's parks department about using a certain park for a day and the cost/reservation. Next, start asking around for volunteers to help. Choose a cause that you and people in your town all care about. Stay away from controversial topics such as lgbt pride or anything political. This will give you poor results with some supportive people and other people badmouthing the event. Once you have a cause chosen, advertise it and ask about volunteers. Create flyers saying "volunteers needed" with a brief summary of the event and contact information. Put these flyers anywhere you can, stores, parks, etc. It might even be worth it to advertise in the newspaper. When you have the volunteers you need, make posters and flyers about the concert itself. Again, put these in public places as well as a newspaper if it's not expensive. From there, you can throw a concert that brings the town together, raises money for a good cause, and it's good for local artists.