Using spark components in a .fla

I'm trying to use Spark components in a Flash Professional CC project. I've added AIR 14 to Flash CC:

and I've adjust my preferences to use Apache Flex SDK and pointed it to paths of Flex additional libraries:

Now, I can add spark components to my project:

import spark.components.Button;

var btn:Button = new Button();
btn.label = "Test";
btn.x = 300;
btn.y = 300;
this.addChild(btn);

but when I run it, it doesn't show them. What it's wrong?

PD: Sorry about my poor English