I found a Z80 CPU lying around my house. I've search all over the Internet but I still don't know how do I input stuff and tell it what to do. Help me please
Unless you want to build a barebones/simple computer basically from scratch, I'm not sure there's really much you can do with just a CPU chip on its own. Maybe there are some simple tests you can run without having a full computer built up around it, or maybe not, I don't know, but you won't really be able to use it as a processor without building most, if not all, of a computer around it. If you just want to see if it works you could find an existing Z80 computer that uses the same package/etc. for the Z80 CPU and swap them out (that would obviously require desoldering the existing Z80 and replacing it with yours, unless it's socketed).