Monitor setup with soundcard?

I'm new to using monitors, as I've been monitoring with headphones for years since I started recording, so I have some questions I need help answering...

How does everyone have their monitors set up for their studio?

I'm looking to purchase either the E-MU 1820M or Echo Layla 3G interfaces for my new setup and was wondering how the heck powered monitors get hooked up to these cards for audio playback/monitoring.

Can anyone explain to me how they hook up? How does this stuff work?

Thanks!