This is a multi-use trail, allowing backpacking, mountain biking, and snowmobiles.
There is a fee to enter the park. Visit the Interpretive Center at the trailhead.
The trailhead is by the Salamonie Interpretive Center in Lost Bridge West State Recreation Area (SRA). The trail wanders through fields and woods to Mt. Etna SRA. It is posted as 13 or 14 miles depending on where you look; I got 12.17 miles on my track. Regardless of length, the trail is well marked using road type signs to warn bikers and snowmobilers of direction and terrain changes.
Trail crosses some fields so you are in the sun for a few miles, but there is also some nice sections next to the lake.
Reference the Indiana DNR Salamonie Lake Bloodroot Trail brochure for pertinent information.