First, welcome to the forum. When you get a minute, drop by the intro thread and say howdy.
Delighted to see someone working with introducing folks to the fun side of plinking!
We could make dozens of suggestions, but will make one instead- the NRA has a section that deals with advice and guidance on setting up and operating ranges. Give them a try- think the toll free number is 1-800-672-3888. If that does NOT get you some help, come back by and let us know.