Planning to do car audio speakers and head unit, what must I buy to do it myself?

I own a 1996 New Yorker and have bought speakers and head unit for it and am saving up for a subwoofer or two. Not sure how to go about putting it all together just working with the speakers for now what do I need like what kind of wiring or whatever? I know how to install a head unit but as for speakers should I put them inside the door where the old speakers are or like in the trunk or in the floor board and just put somethign over it or what? Anything like that would be so extremely helpful thanks so much.