On my machine it starts right up, but maybe your defaults are set differently.
The window on the page wherein the video is cued up has the usual vid box controls at the bottom of it. Just click the triangle at the bottom left of the box, and it should start up. If you have a slow connection, you may want to click the double lines that appear after the triangle is clicked and wait until you have some red line showing next to them, then click again to watch. The red line indicates how much of the vid is loaded. On a slow connection the more you load before you watch, the smoother it will run.
youtube is free, though you can buy a premium acount to be able to upload more.
NightMist