You need to purchase a trail pass at the trailhead, $5 daily or $20 annual as of 2013.
The trailhead is at the South end of the parking lot with an informational kiosk. Buy a trail pass to use the trails. Starting out on doubletrack, the route quickly drops into 9 miles of fast flowing singletrack. The terrain is rolling hills with a few sharp climbs but no real technical sections.
You'll be in dense forest for most of the ride on a 4,000 acre preserve with not many landmarks so you might get a feeling of being lost in the woods but the one-way trail system is well marked and well maintained to keep it up to IMBA standards.