The smaller tubing decals go on the fork legs at the top, just below the crown.
The large tubing decal goes on the forward side of the seattube at the very top. Just below the lug.
The made in Italy goes on the forward side of the seattube, just above the bottom bracket.
The Ernesto signature decal goes on the right side of the top tube, towards the back.
The logo goes on the headtube.
The big vertical Colnago decal goes on the seattube.
The other big one on the downtube.

BTW, who was the eBay seller? Do they have more? My Oldnago could use some decals!
Thanks. Dr. D