Original: In the laboratory however, copper (I) iodide is prepared by simply mixing an aqueous solution of sodium or potassium iodide and a soluble copper (II) salt such copper sulfate.
Simplified: Another way would be to react copper (II) sulfate and potassium iodide. This makes copper (II) iodide which as said before breaks down right away to make iodine and copper (I) iodide.