How exactly do you connect your Xbox/Controller to play Xbox live?

Alright alright, I'm a hardware n00b.

I want to live the dream of playing Halo online, on my couch with an Xbox Controller and a headset.

I don't want to hunch over using spacebar to shoot and press CTRL and doing a backflip to launch a grenade.

After I purchase the Xbox Live Membership and I want to play..

How do I connect my Xbox controller or.. simply my Xbox.. to everything?

xD