The extra 6 holes "W, X, X1, X2, Y, Z" begin after hole #15. To play them, the Blue tee for W is near #16's Blue tee, the White tee for W is back and to the left of #15, towards #14's White tee.
X1-X2 are new holes that begin after hole X, take the trail. Play Y after them.
X1-X2 are new holes that begin after hole X, take the trail. Play Y after them.