How to cascade sugar flower onto a wedding cake?

Start at the bottom and work your way up. It will look more organic and balanced that way.

Do I just stick in the covered wires into the cake?

No, wires do not belong in cake, covered or not. You use straws or posy picks. See this thread: http://cakecentral.com/cake-decorating-ftopict-632290.html

Thank you, because I see even on the TV shows they put the wires right into the wedding cakes when they are making them. That is why I asked about it.

I know, I see that too. I see lots of questionable things on many of the cake shows! I'm not talking about the competitions, because they don't actually serve those cakes, but rather the shows shot in the bakeries and shops. Presumably, those cakes are actual customer orders...but who knows. It could all be fake/scripted.