Well, maybe it helps you if I tell you how it works.
SessionStealer creates a server on your network, using your IP address.
Along the normal minecraft server stuff it needs to run the server, it uses something else. Something like Bukkit, a plugin that runs on your Minecraft server.
Scetch made a plugin which allows you to control people on your server and kind of "hack" into their Minecraft game and if that person is also active on another server, it can run commands through your server, to that person and that person runs the command on another server.
Your question that you're stating is a bit big to say "okay do this and you'll have it running".
Let me say this though: if think you don't know shit and you're just doing something, do NOT and never AGAIN run SessionStealer.
Because SessionStealer is one of the easiest to use programs if you have a full-grown mind (and not one of <16 yo).
Ask your questions, and maybe one will be wise enough to explain you how this piece of software works.
But don't count on it.