From the trailhead follow the path as it heads south. At the intersection take a left to ascend the mountain via the southern trail. Since this is a loop, both trails lead to the summit, but the southern trail ascends a gentler grade due to the numerous switchbacks. Summit Mt. McCoy and enjoy a snack and a rest by the cross, you'll to enjoy great views of Simi Valley, Simi Peak, and the Reagan Library while you do. To descend, head east from the cross and down a much steeper and shorter section of trail. If the grade is too steep runners can also descend by returning the way they came.
If you're looking to extend your run, from the summit you could take the Reagan Library Connector trail to the library.
Thanks to John McKinney, The Trailmaster, for sharing this trail description. To learn more about trails in California, check out his guides at The Trailmaster Store