Yeah, I have a bunch of different shading pencils as well that I got for a gift. I only ever use a 4H to sketch out something first, then trace it with a HB. I don't always do this, however, especially if I feel the 4H came out dark enough. I am in no way an expert on these matters, this is just what works for me.
They're basically meant for shading. With a range of different pencils, you can shade all the way from very light grey to very dark black. Your gallery looks like it's all lineart, and having different pencil hardnessess doesn't do you much good for lineart. But now's a good time to give shading a try, since you have the supplies!
I would note that you have all dark, soft pencils, and no light hard pencils like a 2H. I personally don't like 2H at all, but it may be hard to shade very light areas without them.