Yes. the two halves go around the pipe and the finned clamp slides over.
First get the new copper gaskets in place. I use a VERY small amount of grease to keep them from falling out. The grease will heat up and burn off the first few times you ride, so there may be a little smoke, but it shouldn't be obnoxious.
Then move the header up into position and slide all 4 collars up past the downtubes, but not over the studs. Then put the 2 piece sleeves over the pipes, long side towards the engine, then fit the collars over the sleeves and studs.