First, bring 6 bucks with you unless you have a state parks season permit sticker on your windshield.
After you pass the entrance gate you will encounter a 4-way stop sign. Straight through takes you to the swimming beach. If you take the left turn and follow it a short distance you will come to the marina channel. I haven't seen it for about a month or more, but I bet it's pretty low right now. When the water's high, the channel yields trout, catfish, and a few white bass and walleyes.
Heron Cove I can't help you with, I have a map of Boyd but there's no Heron Cove marked on it.
If you turn right instead of left at the 4-way stop, you go over a small hill and past the campground entrance, and finally dead-end in a small parking circle at the Heinricy inlet. Heinricy lake is the small lake visible just to the west of the inlet. It has bass and crappies in it, but no record breakers.
If you park there and walk south over the bridge and down the paved jogging path for about a quarter mile you will come to a chain link fence, and a foot path out through the weeds to the left, that will lead you out onto a rocky point that surrounds the pump house. There are usually fish to be caught in the channel in front of the pump house inlet. Sometimes trout, sometimes crappies, almost always bass and catfish. Outside the channel, it's shallower and mostly populated by perch, small bass, and undersize walleyes.
Good luck. IMO, Boyd is a hard lake to understand. Every time I catch a lot of fish, and think I finally have the place nailed down, I go out there the next time and it makes a liar out of me. I think the only real solid conclusion I have made about Boyd is that I need a boat.
W. E.