How to tell contract manufacturer which component goes where?

Manufacturing
21

Assembly drawing or Pick & place form ODB++ format would be essential.
Things that the CM expect from you:

  1. Drills and cuts gerbers
  2. Copper gerbers
  3. Soldermask gerbers
  4. Silkscreen gerbers

Fab drawing (Construction summary and board specification details)
IPC 356 CAD netlist

For assembly
BOM
Paste gerbers
X and Y data
Assembly drawing