This is a paid trail. While no one will likely stop you, please pay the fee at the trailhead or purchase a park pass from the lake office.
The trailhead is located at the entrance for the Park Headquarters/Lake Overlook. You do not have to pay a lake entrance fee at this entrance. There is one main trail (red trail) with several detours for a different experience (blue trail). This trail is mostly shaded and the only real obstacle is tree roots. My favorite part starts around mile 3 in what's called the "Swamp Trail" portion. It ends 6.5 miles on at North Midwest Blvd. This trail is great for beginners (it was my first) as well as people looking to add some speed to their hikes.