The two slanted firebrick are an air out. Air comes in the back left on mine if facing the stove (the metal piece where there is no firebrick is an air in. As for installation, i just built a sheet metal box around mine, and put a duct on the top with a duct fan in it to blow it into a register. We will need a bunch more information to help, like what kind of existing system do you have , can you tap into that for distribution, is it in the basement, etc. Doesnt the f.a. come with mounts and brackets to use hitzers furnace box and a fan for distribution?