I usually park close to the ranger station and hit a few fire roads that connect to some old equestrian trails as well as some singletrack. Nothing is marked around this area but there are a few marked trails on top of the mountain that are primarily hiking trails to the lake from various camping spots.
From I-81 go west on RT.9 (exit 16W) and go approximately 15 miles or so and then a left onto back creek vally road. There are signs for the park as well. You will travel on that road to a town called Jones Spring. Once through that town begain looking for the park sign on your right. This is also directions to the lake.
http://www.singletracks.com/item.php?c=1&i=4359