Do you want to copy the whole contact, or just addresses from it?

To copy the whole contact, drag it from the original list to the new one,
hold down Ctrl, and then release. If you don't hold down Ctrl you'll move it
rather than copying it.

To copy just an address or other info, highlight it, press Ctrl+C (to copy),
place the curser where you want it in the new contact, then press Ctrl+V (to
paste).

HTH

Mark