Stand the couple next to each other, point camera at them, press shutter release.
More specific questions will get you better answers, which bits in aprticular are you worried about, e.g. what equipment to use, flash or no flash, organising people, what list of shots should be there, how do i interact, are you in a tudio if so what lighting setup etc.
What type of setting is going to be? Family, friends... a kegger? In all seriousness... if you can give some more detail you'll get much better responses.
Just be ready... if the answer is "No." the photo ops will double at least.