The day before or the night before you are going to serve, mix all the ingredients together for the ambrosia and chill.
The next day, make sure mixture is not watery. If the pineapple is drained to a dry consistency it won't be watery. If it is please drain.
Before you are going to serve about, 1 or 2 hours before, get out a fancy cake dish and then cut the cake in half, put the bottom half of the cake on the dish, then cover with enough mixture to cover the bottom half of cake.
Put the top of the cake back on and cover the top with the ambrosia mixture. (You may have some leftover to enjoy later.)
Refrigerate after assembling.
Just before you are going to serve, frost the sides of the cake with cool whip or whip cream and make a few dollops of cool whip or whip cream on the top of cake.