How do I assign a Class to an element on the Stage? (Edge Hero)

I'm trying to use the Video Time Trigger listed on Edge Hero but I'm having difficulty getting the video to load. In the instructions, it says
"to add the video, i just drawn a rectangle in edge animate and give it the classes videolink_1_mp4 and videolink_1_webm and in Stage action link the files to those classes"
I drew a rectangle on the Stage, but I can't figure out how to assign a Class to it. Any ideas?
Thanks