How do you plug in an audio into a plasma?

Depends on what you mean by audio,

if you mean audio as in the 3 cables that connect into your tv (i.e red, yellow and white) then attach the red and the white (as they both control stereo sound)

If you are on about hd cables then attach the blue and green cables into the appropriate sockets in the back of the plasma screen.

If you are on about audio hi-fi or audio system then use the twin cable and plug both ends into their appropriate sockets

Jackson, =D