This is just a few feet from where you've parked. Stand with your back to the campfire site (facing away from the lake); you'll see the creek bed slightly to your right—it's normally dry after early spring, and that's where I recommend you start—or you can take the trail immediately in front of you, but it's a little misleading doing that because it soon peters out, at which point you'll need to go right so as to pick up the creek bed (it's quite close—only a few feet), then you'll be okay. It's just easier to start up the creek bed from the beginning, is all.