You'll need to use the Cliatt Creek Nature Trail Loop for access to the Rock Dam Trail. Rock Dam Trail is a dirt singletrack through a heavy forest in Mistletoe State Park. The first part of the trail follows the banks of Cliatt Creek, and you'll have views of Clarks Hill Lake from the northern reaches of the trail.
Most of this trail is relatively tame, but there are quite a few creek crossings and a few of these will challenge even advanced riders. The namesake Rock Dam (you'll know when you get there) creek crossing is rideable by expert riders, but keep in mind the rocks will be slick when wet.
Another advanced feature is the gully ride, which is right before the rock dam in the counterclockwise direction. You can also look forward to some challenging climbing on a cross-sloped, root-laden section on the northern side overlooking the lake.