This obviously isn't a substitute for an informative site, but the basic principles are:
1. Set shutter speed at or below camera sync speed. How much below depends on how much ambient light you want to let in.
2. Use light modifiers to shape the light from your flash the way you want it.
3. Aperture determines flash exposure at a given ISO. Meter and use f-stop ratios, or just adjust the power settings on your flash(es) to taste to get the flash exposure correct.